Ann Cryer wept when she heard the news last week. "It reduced me to tears, reading all that went on in Rotherham," she said.

"The really sad aspect of it is that many of these girls could have been spared. If only I had known what was going on in Rotherham, I would have had a better understanding of the widespread nature of the problem. Instead, I simply thought it was a purely local issue that emanated from Keighley … If I'd known, I could have said, 'We need a national policy on this.' I was on [the Labour party's national executive] at the time, so I would have been in a good position to press for that. But no one talked about it."

In 2002, when she was Labour MP for Keighley, Cryer became the first public figure in Britain to talk out about allegations of "young Asian lads" grooming underage white girls in the West Yorkshire town. As a result, she was shunned by elements of her party, a panic button was installed in her house and Nick Griffin stood against her for the far-right British National party (BNP), claiming that she was not doing enough to protect young white girls.

Cryer's battle began when seven mothers came to her to claim that their daughters had been groomed by young men from the Pakistani community. "They said the girls were being used for sex by them and handed around – not as prostitutes, but were being handed around the families of these lads. This was underage sex. These girls were well below 16. The mothers said, 'We understand it's a criminal offence even if it's consensual', which I said was quite right. And they said to me, 'Why is it that West Yorkshire police won't do anything about it, social services won't do anything about it, when we have given them the names and addresses of the men abusing our daughters?' "

Twelve years on, Cryer described these women as "enlightened mothers, members of the Labour party, women who I would never in a million years have described as racist".

Yet no one wanted to know. Cryer said she had "constant" meetings with West Yorkshire police and social services, only to be told there was no point trying to mount prosecutions. She claimed: "They found constant excuses not to do anything. You would think it would be clear-cut – these girls were too young to consent – but police kept saying it wouldn't get to trial because these girls wouldn't give evidence," she said. "They thought these lads were their boyfriends. They thought they were going to get married. But no. Most of these lads were already married to a cousin from Pakistan."

Frustrated that neither police nor social services wanted to help, Cryer tried a different tack. In parliament, she worked with then home secretary David Blunkett to make grooming a sexual offence and to encourage courts to accept third-party evidence in cases where a vulnerable victim would not come to court.

In Keighley, she tried to get the Pakistani community on side after learning that the News of the World had offered the seven mothers £1,000 to tell their story. "I thought, if this happens, knowing the way the News of the World would handle it, it would cause chaos and ruin any sort of race relations that we had. We could have race riots, the works."

So she asked a friend, a Muslim councillor of Pakistani heritage, to approach the elders at the mosque with a list of 35 names and addresses of the alleged perpetrators. "He said to the imams, 'Ann Cryer would like you to go around to these families and explain that this behaviour is totally un-Islamic.' But the upshot was that the elders allegedly said, 'Go back to Ann Cryer and tell her it's nothing to do with us.' "

Desperate for community tensions not to be inflamed by tabloid reporting, she persuaded Channel 4 News to produce a report. In 2004, five of the 35 men were sent to prison. Cryer said male colleagues in parliament privately congratulated her on her courage. She wouldn't name names, but said: "What male MPs from similar areas to Bradford and Keighley would say to me from time to time was, 'Oh, you're so brave taking up these issues' – either forced marriages or grooming of girls. I would think, 'Well, it wouldn't need so much bravery if people like you would support me.' "

Last week, Denis MacShane, the former MP for Rotherham, admitted he might have not done enough about child sexual exploitation by Asian men in his constituency because he was a "Guardian-reading liberal leftie". MacShane, who resigned as an MP in 2012 over expenses fraud for which he was later jailed for six months, told the BBC he was never directly approached by anyone with allegations of child abuse during his 18 years as an MP.

Yet he "probably" didn't do as much as he could have done and should have "burrowed into" the issue, he said. "I think there was a culture of not wanting to rock the multicultural community boat, if I may put it like that." Last week, he said Cryer did what others should have had the courage to do. "If you read my prison diaries, I praise a lady, an MP called Ann Cryer, who did raise the problem of cousin marriage and patriarchy, of the oppression of women within bits of the Muslim community in Britain."

Cryer is adamant that she can't have been the only politician to have heard such stories. "There must have been councillors and MPs, I think, all over the country who knew what was going on but were terrified. It's a genuine fear, to be terrified of being labelled a racist. No one wants to be called a racist, least of all someone who isn't a racist."

Yet that's exactly what happened to Cryer, an insult compounded when Griffin decided to contest her seat in the 2005 general election for the BNP. "His reason for challenging me: 'She didn't do enough to protect those white girls'," remembered Cryer. "That was nonsense. I'd almost killed myself trying to protect them." Griffin lost, polling just 9.2% of the votes to Cryer's 44.7%, but police were worried enough about Cryer's safety to install a panic button with a direct line to Shipley police station.

When Keighley's problem was out in the open, she claimed to have talked about the issue with Ken Livingstone, then mayor of London, at City Hall. According to Cryer, "Ken was convinced I had got it all wrong. He was so politically correct, he was off this planet at that time, was Ken."

Livingstone said that he had no recollection of that meeting, but that "if she said there was a meeting she clearly wouldn't be lying … I'd say then what I would say now, which is that paedophilia is clearly fairly prevalent in every culture and faith, depressingly much more than we thought. The idea that Islam would be exempt from paedophilia is rubbish."

Seeing Rotherham's shame on the front pages made Cryer think of her struggles as she sought to get a hearing for the concerns of her constituents. She wondered what her detractors from 12 years ago made of it. Were they thinking, "Maybe Ann Cryer was right"?

"To tell you the truth I don't give a damn," she said. "I'm nearly 75 now, I'm out of it all. But the feelings linger on for how wrong it was for people to misjudge me in this way."