I arrive at Sadiq Khan's office in Tooting, south London, to find the shadow justice secretary chatting with one of his female constituents in Urdu. Khan is one of 19 Asian MPs and was the first Muslim to attend cabinet. "I don't call myself a Muslim MP," he tells me. "I'm an MP who happens to be Muslim."
Khan has been MP for Tooting, where he was born and brought up, since 2005. Last year, the Tories - bolstered by Lord Ashcroft's millions - targeted the seat; Khan's majority was slashed by nearly 3,000 votes. When his re-election was announced by the returning officer in May, his supporters chanted "Yes, we Khan", in the manner of a Barack Obama rally. "We were the seat that the Tories needed to form a government," he says proudly.
Khan's unlikely victory in Tooting was followed by his appointment as campaign manager for the Labour leadership bid of Ed Miliband - whose victory, too, was against the odds. In October, Khan, a former civil liberties lawyer, was elected to the shadow cabinet and given the role of shadow justice secretary. He was charged with shadowing two of the coalition's biggest beasts, the Justice Secretary, Ken Clarke, and the Deputy Prime Minister, Nick Clegg (on constitutional affairs). Young and articulate, he is a card-carrying member of his leader's "new generation".
Born in 1970 to immigrants from Pakistan, Khan was the fifth of eight children - he has six brothers and one sister. He grew up on a council estate. "It was crowded," he tells me. "There were two and a half bedrooms." His father was a bus driver and his mother sewed dresses. He did not go abroad until he was 23, when he went on holiday to the United States.
“Class is still relevant," Khan says. "I don't think we should pretend it isn't." However, he dismisses Labour's antics in the Crewe and Nantwich by-election of 2008 - sending out activists in top hats, dressed as toffs - as "crude" and "not smart politics". He is keen to warn against the conflation of "aspiration and class". "Labour has got to be careful if it is to carry on being the party of aspiration," he says.
What about the coalition? Does it matter that there are 22 millionaires in the cabinet? "That they are rich is relevant because of the lack of empathy. I'm not saying that they can't empathise - but they just don't get it.
“For them, tightening your belt is taking two holidays a year instead of three . . . or having one au pair rather than two. I think it is a problem if you have a cabinet that doesn't understand the real challenges that people face. If you have a background that is one-dimensional and have not had the life experiences or understood what sacrifice means to ordinary punters, I would say it is difficult." He then hastens to add: "I'm not saying you can't empathise without experiencing things - but it is difficult."
Does he consider himself to be working-class or middle-class? "I am middle-class by profession, but I hope I've not forgotten my working-class roots."
I point out that there are few politicians with working-class roots left on the Labour front bench after the former postman Alan Johnson's resignation as shadow chancellor. Khan nods. "Johnson going is not only a huge disappointment. Very few of us in the major parties have diverse experiences and that is a problem. We are going backwards."
Khan mentions the potential impact of the new, austere MPs' expenses system, overseen by the Independent Parliamentary Standards Authority (Ipsa). "One of the unintended consequences of Ipsa will be that you will end up with people who are independently wealthy, or who haven't got any dependants, or whose families need to live hundreds of miles away, while they are living by themselves in Westminster." He smiles, before adding: "And we know all the mischievous behaviour that can cause. It is inevitable that politics will become a middle-class vocation, which is dangerous . . . we, as a party, need to do more and the trade unions have also got to step up to the plate."
But isn't he embarrassed about how elitist Labour seems to have become? Three of the top posts in the shadow cabinet - the leader, the shadow chancellor and the shadow home secretary - are held by middle-class Oxbridge graduates who spent much of their pre-parliamentary careers as special advisers.
“I am not saying that there is anything wrong with wanting to be a politician," he says. "What I am saying is that it is not a good thing when you have all three parties in parliament filled with career politicians."
Given his background, how did Khan end up as a lawyer? "LA Law," he replies, referring to the hit US television drama series of the 1980s. It starred, among others, the Hispanic actor Jimmy Smits as the dashing young attorney Victor Sifuentes.
Khan cites the character of Sifuentes as an inspiration (he pretends not to hear me when I remind him that Smits went on to play the US president in The West Wing and I ask him whether he has similar leadership ambitions). "Don't underestimate the power of TV. In LA Law, you had these lawyers acting for underdogs, doing these great cases, and I was reading in the newspapers about the Guildford Four, the Birmingham Six and all those miscarriages of justice. Those were my formative years."
What prompted him to specialise in human rights? "Acting for the underdog," he says. "When I was growing up, I saw friends' big brothers being stopped and searched by the police; people losing their jobs; my dad's garage under threat of closure. I needed to be useful."
When he was 26, he founded the law firm Christian Khan with Louise Christian. He went on to serve as chair of Liberty, where he played an influential role in appointing a young Shami Chakrabarti to lead the organisation in 2003.
He "walked away" from his firm in 2004 to become a prospective parliamentary candidate in Tooting, where he had been a member of the local Labour Party since the age of 15, because he wanted the opportunity to change "hundreds of thousands of people's lives" as a member of parliament. "I didn't have any mates who were already MPs or ministers when I went into the Commons. I went in there as somebody whose CV and backstory was [about] taking on the party." Khan reminds me that he voted against Tony Blair's 90-day detention-without-charge proposal as a freshman MP in November 2005; I remind him that he later voted in favour of ID cards and the renewal of control orders.
Did he feel that he had sold out his former colleagues who were still working in the field of civil liberties? He shakes his head. "Politics is about compromise. We don't have à la carte politics in this country."
In a forthcoming Fabian Society event, Khan will deliver his first major speech on the party's approach to criminal justice. Like Ed Miliband, he is dismissive of the triangulation and authoritarianism of the New Labour years. "I think one of the things that a Labour home secretary and a Labour lord chancellor found difficult was to get out of a Daily Mail headlock. We allowed that tail to wag the dog." Does prison "work"? "It depends what the purpose is. If prison is to punish, it does . . . It doesn't rehabilitate enough, though." On the subject of Islam, I ask whether he agrees with the Conservative Party chair, Sayeeda Warsi, who is a fellow Muslim, that Islamophobia has become acceptable in Britain.
Khan describes the Tory peer as a "mate" but says that her recent speech was "too simplistic". "My view is this. When I speak to my cousins in Pakistan, they tell me that no one from my family could dream of becoming a member of parliament there, let alone a member of the cabinet. That I could in Britain is a huge source of inspiration to them."
So, is there no Islamophobia problem in the UK? "Of course there is. I think we are now at the stage where the Afro-Caribbean community was 20 years ago and the Irish were 30 years ago." (On 5 February - just two days after our interview - Khan accused David Cameron of, in effect, "writing propaganda" for the English Defence League by denouncing both Muslim extremism and multiculturalism in a speech to a security conference in Munich. Khan's "mate", the Tory chair, accused him of "outrageous and irresponsible" smears against the Prime Minister and demanded that he apologise. He hasn't.)
Was he surprised by his friend Miliband's victory in the Labour leadership contest in September? The night before the result, Khan told Miliband to "prepare for defeat". "I learned this from Rumpole of the Bailey," he says. "Always tell your client he's going to lose because, if he loses, he's expecting it; if he wins, you're the fantastic lawyer who got the victory." However, he adds: "I had a feeling we'd done it."
How does he respond to his backbench colleagues who have been grumbling about their leader's "slow" and "shaky" start? "They need to get a sense of perspective. We're in the ninth month of a 60-month parliament. Blair had three months before his first conference speech and they knew there'd be an election by May 1997." In contrast, he says, "we've got five years to go. The important thing is that Ed continues to improve."
Is he worried about the dynamic between Miliband and Ed Balls, the new shadow chancellor? Is Balls "on probation", as one shadow minister put it to me? "As somebody who aspires to be lord chancellor, I believe in rehabilitation and giving people another opportunity," he says, laughing. "I judge a person as I find him and, on the evidence I've seen, Ed Balls is a brilliant shadow chancellor."
Khan is an astute politician. I ask him what he thinks is the main challenge facing Labour in opposition. "Many of us have friends and family [members] who, in the past, would have said that they were Labour voters but now feel uncomfortable about being Labour voters, even though they voted for us in 2005 and 2010. We need to change that. You should vote Labour with pride."