Standing on a dusty street under the Karachi sun, already blazing at 9am, it strikes me that I am being rejected. I am at a Christian-run school, amongst a crowd of parents vying for appointments to secure admission for their children. The reception, if that is the word for it, is a hatch in the brick wall, behind which sits a harried looking man with a stack of papers and a phone. After wrestling my way to the front, I explain that I am here to talk to the headmaster about religious discrimination.

The man phones the headmaster's personal assistant. I explain my connection to the acquaintance that told him to expect me, and tell her that I'm researching Christians in Pakistan. After nearly 10 minutes, standing on the pavement with the phone cord pulled awkwardly out into the street, I realise that the line has gone dead and she's hung up the phone. The man behind the desk is distinctly unimpressed, given the crowd amassing behind me. Convinced the line has been accidentally cut off, I ask him to call again. The PA's tone is markedly different. "You're not the only person I'm dealing with," she snaps. "The father doesn't have time for all this."

When I speak to my acquaintance later that day, he shrugs. "Don't be offended," he says. "He is prominent so he is easily identifiable. Are you surprised he is scared to talk?"

Pakistan was conceived as a secular state with Islam as its main religion. "We have many non-Muslims -- Hindus, Christians, and Parsis -- but they are all Pakistanis," said the country's founder, Muhammad Ali Jinnah in a celebrated speech. However, in the late 1970s and 1980s, the military dictator General Zia-ul-Huq engaged in a repressive programme of 'Islamisation'. Among his actions was the introduction of a set of blasphemy laws, under which a person can face indefinite imprisonment or even the death penalty for criticising the Prophet Muhammad or the Qur'an.

The current debate is not about the existence of the law itself (many countries have blasphemy laws, as did the UK until 2008), but about the exceptionally harsh penalties and the very light burden of proof. Hardly any evidence is required - the accuser can even refuse to repeat the blasphemy in court for fear of committing the crime himself - and so the law is frequently used as a means of settling personal scores or stirring up sectarian tension.

The issue came to international attention last November, when Aasia Bibi, a Christian mother of five, was sentenced to death for "insulting the Prophet". The remarks were allegedly made after co-workers refused to share water that she had carried, on the basis that Christians are unclean. Throughout her trial, she did not have access to a lawyer.

Aasia's case was taken up by three politicians in the ruling Pakistan People's Party, who called for reform: Salman Taseer, the governor of Punjab (Pakistan's most populous state), Shahbaz Bhatti, the Minorities Minister, and Sherry Rehman, a prominent backbencher.

The consequences speak for themselves. On 4 January, Taseer was shot dead by his own bodyguard outside a coffee shop in Islamabad. On 2 March, Bhatti too was shot by assassins from the Pakistani Taliban. Rehman is living in semi-hiding in fear for her life. And on 2 February, soon after Taseer was killed, the prime minister, Yousuf Raza Gilani, told his government that he would not touch the law and that all reform would be shelved: "We are all unanimous that nobody wants to change the law."

It is easy to see why people might be afraid to speak out in favour of change. Taseer's daughter Shehrbano is a recent graduate working as a journalist for Newsweek in Lahore. "Very few people condemned my father's murder," she tells me when we speak on the phone. "Everyone was so petrified that they'd be next. That's how terrorists operate. The night that my father died, I thought, OK, this is going to be a huge watershed moment in the history of Pakistan. But the complete opposite happened. We went ten steps back."

This anger at the government's handling of the assassinations is shared by many. "I feel very strongly about it, of course I do. But I won't say anything because I don't want to get shot," a diplomat tells me. "Even my servants could betray me. It was his bodyguard - a servant - who shot him."

There is a real sense of fear among the ruling classes. One evening, a PPP former minister tells me that he hates the idea of having an armed guard and drives himself everywhere - but keeps this fact to himself, and makes sure to take different routes and not to travel at the same time every day.

Caste out

About 96 per cent of Pakistan's population is Muslim. However, the 4 per cent minority of Christians, Hindus and Islamic sects such as the Ahmadis (regarded as non-Muslims) translates to nearly ten million people, the equivalent of the population of Tunisia.

Well before the Taliban became a political force in the country, minorities faced serious social discrimination. I speak to Sujawal Massey, a Christian man who works as a sweeper - one of the lowest-status jobs there is. Aware of his position in this acutely class-bound society, he does not sit down, but hovers awkwardly as we talk in the living room of the lavish house where he works, looking at the floor except when spoken to.

He tells me it is difficult to find work. "They don't let us move ahead. We get no chances. If they know you're a Christian they say: there's no room here for you."

I ask what impact this has on a day-to-day level. "If we end up somewhere where there are Muslims, we're in trouble if they discover we're Christian," he says. "We don't tell them we're Christian in the market, because they won't give us anything. They won't even let us drink from a glass."

His employer tells me that while she insists that he is fed with the other servants (most of whom live in quarters in the house) many of her friends do not do the same for Christian members of staff. She keeps separate utensils for him to eat with, because her Muslim servants are unwilling to share theirs with him.

The reluctance to share water was also central to the Aasia Bibi case. "It is a carry-over from the Hindu caste system - the idea of untouchability," explains Dr Theodore Gabriel, a University of Gloucestershire academic and author of a study of Pakistan, Christian Citizens in an Islamic State. "Most of the Christians in Pakistan come from a low caste. The 'untouchable' or Dalit class were targets of missionary activity during colonisation, so they have come from a low economic and social background."

This social persecution remains in place even for those who have worked their way out of typical 'untouchable' jobs. I visit a beauty salon in an affluent suburb of Karachi, owned by a Christian Pakistani woman, Jane Peters. The shop is busy, with several Muslim women waiting to be seen.

However, all is not well behind the scenes. "There are terrible problems," she tells me. "I pay my bills, I pay my taxes, but the neighbours have had the water supply cut off." This means that she cannot get running water to the shop, and instead has to buy it in tankers each morning and manually heat the water required for hair-washes and manicures. The process of giving treatments is delayed by staff having to carry kettles and basins of hot water up and down stairs.

The shop is staffed entirely by Christian girls - "otherwise there are quarrels," explains Peters - and so it provides a rare employment opportunity for those who would otherwise end up in menial positions. One of the girls tells me that she quit school prematurely so that she could take the job, and is trying to complete her education part-time. "It is very hard for us to find employment," she says.

No change

It goes beyond sharing water. Gabriel describes school textbooks which claim that Christians worship three Gods, and define citizens of Pakistan as Muslims. "That means Christians are not regarded as citizens - if a textbook says that, then that is what children are learning. It's not going to foster tolerance, is it?"

Speaking to Christians, I am struck by their acceptance. "People are afraid," explains Peters' daughter, Sabiha, an articulate young woman who speaks fluent English. "If we make a fuss, it's very easy for someone to accuse us of blasphemy. It affects the poorer communities more, but it is a worry for everyone."

This type of discrimination is deeply entrenched, given that it pre-existed the formation of Pakistan by more than a thousand years. But is it worsening given the increasing influence of extremist ideas? Many view the decision to shelve reform of the blasphemy law as a victory for the militants. The women in the beauty salon - educated and politically aware - share this view. Yet when I asked Massey whether he was afraid and if he felt his situation could be improved, it was clear that the world of law and reform was alien to him.

"We are very few in a big nation, so we try to stay out of trouble," he says. "Maybe someone can help but we don't know who there is or is not. Politicians don't give us any importance." During the interview, my interpreter wells up. Later, she tells me that she was distressed by his total acceptance of the status quo.

This social discrimination is intensifying, says Ali Dayan Hasan, country director for Human Rights Watch in Pakistan. "Empowered extremists are making more frequent use of the legal tools at their disposal to persecute minorities. They are also killing them with impunity in a way they haven't done before."

He explains that rising extremism means that minorities are increasingly targets. "The militancy is contributing to it, but the fact of the matter is that the structure of these legal frameworks essentially makes the Pakistani state a partisan, sectarian actor, rather than a neutral arbiter between citizens. That tilts the balance in favour of the persecutor rather than the persecuted."

It appears that there is no real appetite for change. Most of the Muslim Pakistanis I speak to agree that there are problems with community relations, but prioritise other concerns.

"We have no human rights," says Iqbal Haider, a human rights lawyer who served in both Benazir Bhutto's governments, slamming his glass down on the table. "If I don't have the right to survive, all other rights are meaningless. And if the majority is not safe, then how can you expect the minorities to be? Nobody is safe."

He draws attention to the thousands of lives lost to terrorist attacks in the country since the beginning of the 'war on terror'. The death toll is rising each year and currently stands at record levels. "The Muslim places of worship are not safe. This is the greatest tragedy of Pakistan," he shouts. "Forget about the Christian church, forget about the Hindu temples. Muslim mosques are unsafe." Several days later, a big attack on a Sufi shrine in the Dera Ghazi Khan district kills 40 people.

While many Pakistanis brush over the impact that the government's retreat over the blasphemy law will have on religious minorities, most acknowledge that this refusal to stand behind the reformers handed the extremists a symbolic and practical victory.

"Salman Taseer was not just an ordinary citizen, "says Haider. "He was a representative of the federation. Shahbaz Bhatti was not just a Christian leader. He was a minister of Pakistan. It was an attack on the government. It is a matter of shame that the government is succumbing to this violence, and does not take these attacks as an attack on their existence."

The government's retreat leaves little hope for reform of these repressive laws, or for the introduction of legal steps to penalise discrimination. Moreover, the legislation is just one part of the complex Pakistani state system. "You have a judiciary that is in sympathy with many extremist views, that feels that it is its duty to uphold discriminatory laws," Dayan Hasan explains. "You also have a military that has a historical alliance with extremist groups and tends to view them with a higher level of tolerance. So when we criticise the government and its inaction, which absolutely needs to be done, we have to contextualise it within the framework of the forces arrayed on the tide of intolerance and extremism."

Yet Shehrbano Taseer sees some cause for optimism. "These laws won't go away tomorrow, but something huge has happened from my father's murder - these laws are being talked about. Nobody knew the cases, the stories, the numbers, the origins of the laws. All of this has come forward. It's important that the debate and criticism should not die with him. My father always said it's not about religion, it's not about politics: it's about humanity. He was genuinely concerned about the humanitarian crisis in Pakistan."

Some names have been changed to protect identities

Samira Shackle is a staff writer for the NS