Angélique, a tired-eyed woman in her twenties, seems to be exhausted by telling her story. We are sitting in a greasy London café eating chips and chops, and the more she tells, the more I want to ask. So she goes on narrating, in her lilting French, the story of why she came to this country all the way from the Democratic Republic of Congo a few years ago. Her father was a politician in Mobutu's government, and she grew up in a nice house in the presidential quarter near Kinshasa. But during the civil war that ended with the overthrow of Mobutu, soldiers broke into the quarter and attacked her house.

The soldiers killed her mother and took her to a prison, where she stayed for three and a half years. There she was made the sex slave of the prison governor. "Once or twice a week the guards would fetch me to come to his room and he would rape me," Angélique says. "One night he took me to his house. He did what he did, and then he fell asleep. I started to pray and then to sing. He was oblivious. I went out of the door into the courtyard and took a pail of water and washed myself there in the yard. He didn't move. I looked in at him, and I thought to myself, there are two possibilities if I run now: either they will kill me, or God will save me." So Angélique ran away into the bush, and eventually found her way to the house of a friend of her father's, who arranged for her to get to England.

And there her troubles should have been over, and she should have been able to grieve for her parents in peace and build a new life. But her asylum claim failed, and Angélique was left home-less and forced on to the streets of London. She went to the office of the Refugee Council, and of the National Asylum Support Service, but was told there was nothing they could do for her. She walked from one end of the metropolis to the other, from Archway to Brixton, from Ilford to Hounslow, desperate to find places to sleep and food to eat. One day she met a man who took an interest in her and gave her a bit of money. "That evening I became pregnant," she says. "Then I had real problems. I got cramp in my feet and legs." Until she was seven months pregnant Angélique walked the streets of London. Then, at last, she met a member of a volunteer support group who took her to hospital and found her accommodation. Although she now has a new solicitor, she still has not been given asylum.

Was it a unique miscarriage of justice that allowed Angélique, a victim of persecution in the Congo, to end up sleeping on doorsteps, a victim of our total indifference in London? Sadly, she is far from alone in having a good case for asylum and yet having her claim rejected. Debora Singer, co-ordinator of the Refugee Women's Resource Project at Asylum Aid, says: "When women tell stories even of very real persecution, they are too often not taken seriously by decision-makers."

The failure of an asylum claim is not like most other miscarriages of justice; it puts a full stop to that person's life. Immediately an asylum-seeker fails in her claim, she is made destitute, with no chance of benefits or work. I have met dozens of women, including pregnant women, women with children, young girls and grandmothers, who are living destitute in London. Failed asylum-seekers are also liable to be detained and deported at any moment. Our detention centres hold hundreds of women whose stories are unheard, yet as soon as you begin to talk to any of them you find a woman who should have been given refuge.

One such woman, Bella, is in Yarl's Wood detention centre with her two-year-old son. I met her a couple of months before her detention. Later she described to me by e-mail what made her flee after government agents burst into her house in Uganda to extract information from her father. "One of the men raped me while the other held my father's head to make him watch. His arms were tied. He was beaten each time he closed his eyes. I pleaded for him to give them what they needed, but he did not. I leave the matter open for anyone to conclude whether I have been a victim of torture." Bella has already faced two attempts at deportation, during which her son watched as her arms were twisted and handcuffed behind her back, and she was forced, sobbing, from van to aeroplane.

I am not suggesting that there are no problems with the way that men's claims are decided, but women have particular problems in the asylum system. Decision-makers are not taking their stories of sexual violence seriously, despite good evidence about the way that rape is used as a method of political persecution in certain countries.

Usually, even when Home Office adjudicators agree that sexual violence occurred, women are told this does not add up to persecution for the purposes of asylum law. British asylum law follows the UN Refugee Convention 1951, which states that sanctuary should be given to people who show a well-founded fear of persecution because of their race, religion, nationality, membership of a particular social group or political opinion. Many women who come here are told they do not fall into any of these groups, even when their persecution is clearly politically motivated.

Women come to the UK to seek refuge not only from soldiers and police, but also from their own families and husbands and boyfriends - from persecution such as female genital mutilation, trafficking for prostitution, the forced marriage of themselves or their daughters and threats of honour killing. Farhat Khan, who lives in Manchester, came to Britain from Pakistan, fleeing her husband and his family. She had put up with her husband's violence for years, but the crunch point came when, as she explains: "My husband's mother got my two daughters, then aged five and eight, engaged to her two grandsons. Both men were more than 15 years older than my daughters and were even more violent than my husband. I was horrified at the prospect of my daughters meeting a fate even worse than mine." Her husband has made it clear through other relatives that if Farhat returns to Pakistan the family will take revenge on her for damaging his honour. As an articulate, intelligent woman, she has found great support within her community and beyond; and yet, despite a petition bearing thousands of names, she has been refused asylum.

Even though Farhat's story is accepted by the Home Office, she has been told it does not satisfy the requirements of asylum law. Women are being advised in this way even though some defining cases that have gone to the House of Lords have shown that the judges in the UK's highest courts do believe that women in such situations should get asylum. In a joint landmark case of 1999 - Regina v Shah and Secretary of State for the Home Department v Islam (known as Shah and Islam) - the House of Lords ruled that women fleeing domestic violence in Pakistan should be seen as a "particular social group" for the purposes of asylum law. Other Lords and Court of Appeal decisions have drawn similar conclusions on cases of women at risk of sexual violence by state agents or by private individuals in states where the government will provide no redress or protection. These defining legal rulings, however, are not being followed consistently.

"Overall," says Frances Webber, a barrister who worked on Shah and Islam, "there is a tremendous reluctance on the part of Home Office decision-makers to accept the validity of women's experience - just to believe them. And then, when a woman's claim is believed, it is not seen as grounds for asylum. Rape by soldiers or prison guards is still so often discounted - it is seen as personal, not political persecution - let alone experiences such as domestic violence or honour crimes. We have banged our heads against the brick wall of the Courts of Appeal until we are bleeding, trying to explain how women are persecuted, but there is an institutional refusal to accept the reality of the situations these women face."

What this means, in hard facts, is that women such as Angélique and Farhat are being treated as beggars and criminals when they have come to this country to seek refuge. Frances Webber says: "I believe there is a real battle on hand to get women's experiences respected. A ferocious battle." Given the current fears about immigration, some may think that the fight is unwinnable, but you can perfectly well support strong controls on immigration and still find it unacceptable that a pregnant and destitute refugee should walk the streets of London, that a woman fleeing sexual torture should be held in detention with her young child, or that a woman at risk of honour killing should be returned to her country.

A new campaign, Women for Refugee Women, is encouraging British women to support the rights of women who flee rape and other kinds of gender-related persecution to seek refuge here. Juliet Stevenson, who will be reading the story of Angélique at an event for the campaign at the Institute of Contemporary Arts in London on 16 May, has said: "I think these stories of injustice should be much more widely heard. Then people might raise their expectations of what could be done for these women." Farhat Khan, who will be speaking at the event, says to me: "I still believe that if more women knew about what women are suffering in the asylum system, they would stand up for us."

For more information about the Women for Refugee Women campaign and the event at the Institute of Contemporary Arts on 16 May, e-mail info@refugeewomen.com