Outside Liverpool Crown Court a large group of protesters gathered as the trial began of the nine Asian men from Rochdale who have just been jailed for grooming underage girls for sex. The demonstrators carried printed banners that read: "Our Children Are Not Halal Meat". Some had more improvised, handmade posters saying "Paedo scum", "Lock 'em up" and "Hang 'em".

These were the combined pride of the British National Party, the English Defence League and a couple of other far-right groups – called the North West Infidels and the Combined Ex-Forces. They had been brought together by websites claiming there would be a media blackout of the trial of what they described as "Muslim paedophile grooming gangs" charged with "countless abhorrent sexually motivated charges against children and minors".

Nick Griffin, leader of the BNP and a Member of the European Parliament, was there to give a video interview for the BNP website. "The mass street grooming of young girls from the English community is only being carried out by Muslims. All the paedophile groomers in this particular sort of crime – on the street, in gangs – are Muslims. That's the common denominator," he explained fluently.

"You only have to read the Koran or look at the Hadith – the expressions of what the Prophet did in his life– to see where Muslim paedophilia comes from," he continued. "Because it's religiously justified so long as it's other people's children and not their own." This is pretty poisonous rhetoric. And the BNP website prefaces it with an atmospheric recording of the Muslim call to prayer. Some of the protest placards are written in cod Urdu script. The message is clear.

The overall statistics give the lie to such claims. Greater Manchester Police, in whose area the offences took place, has declared that 95 per cent of the men on its sex offenders register are white. Just five per cent are Asian. But things do look different when the focus is narrowed to crimes involving groups of men grooming girls on the street. In 18 child sexual exploitation trials since 1997 – in Derby, Leeds, Blackpool, Blackburn, Rotherham, Sheffield, Rochdale, Oldham and Birmingham – relating to the on-street grooming of girls aged 11 to 16 by two or more men, most of those convicted were of Pakistani heritage.

Sentencing the Rochdale gang yesterday, Judge Gerald Clifton appeared to give credence to the idea that cultural issues were involved. "All of you treated [the victims] as though they were worthless and beyond respect," he told the men. "One of the factors leading to that was the fact that they were not part of your community or religion."

But the judge also made it clear that such an interpretation should not have too much weight placed upon it. "Some of you, when arrested, said it was triggered by race," he continued. "That is nonsense. What triggered this prosecution was your lust and greed."

With MPs announcing the launch next month of an inquiry into grooming (which will involve visits by home affairs select committee members to Rochdale and other northern towns), the underlying question is more pertinent than ever: are there more Asians involved in this kind of crime than might be expected, as a proportion of the population? And, if so, are there any cultural factors that would account for it? I have spent the past two months trying to pick a path through a thicket of racial prejudice, on one side, and political correctness, on the other, to find an answer to these questions.

Emma Jackson's story is typical. She was chatted up in Meadowhall shopping centre near Sheffield by a couple of Asian boys a year or so older than her. But then she was introduced to their older friends and then to a glamorous suitor called Tarik, who gave her gifts and drinks, cigarettes and drugs, and rides in his smart car. He encouraged her to try the drugs because, he told her, she was old enough, whatever her parents said. She was his princess. He was the only one who understood her: her parents were just fuddy-duddies who wanted her not to have any fun.

But one night Tarik raped her, and everything changed. Confused, and thinking it must be her own fault, Emma was easy prey when he passed her on for sex to other men. She was repeatedly raped, exploited, beaten and told that if she refused to co-operate the men would firebomb her home or rape her mother and make her watch.

Various newspapers have quoted figures complied by The Times which examined the 18 trials mentioned earlier and showed that of the 56 people found guilty of crimes including rape, child abduction, indecent assault and sex with a child, 53 were Asian. Of those, 50 were Muslim and a majority were members of the British Pakistani community. Most of the victims have been white, although in one case several Bangladeshi Muslim girls were also abused. These were reported as being supported by research by two academics at the Jill Dando Institute of Security and Crime Science at University College London (UCL) which examined just two cases, involving 25 offenders.

However, the picture presented by the academics, Ella Cockbain and Helen Brayley, is a lot less clear. "The citations are correct but they have been taken out of context," says Ms Cockbain. "Nor do they acknowledge the small sample size of the original research, which focused on just two large cases." They worried that "findings were being overextended from a small, geographically concentrated sample to characterise an entire crime type". Even their most recent work studies just five cases – though of the 52 offenders involved totals 83 per cent are Asian Pakistani, 11 per cent Asian other and 6 per cent white. That is a very small sample.

So is this a particular problem in the British Asian community? The question touches on so many sensitivities about race in contemporary society that it is hard to find anyone prepared to tackle it clearly and sensibly. Perhaps that is not surprising. When the former Home Secretary Jack Straw raised the issue last year – claiming that "there is a specific problem which involves Pakistani heritage men... who target vulnerable young white girls" seeing them as "easy meat" for sexual abuse – he found himself in political trouble. He was criticised by one fellow MP for "stereotyping a whole community".

Something similar has happened to a support group called Crop (the Coalition for the Removal of Pimping), for the parents of sexually exploited girls. Since 2002 the group, which is based in Leeds, has supported the families of 400 victims, including that of Emma Jackson. Last year it was saying that the families had suffered mainly at the hands of Pakistani men.

"The vast majority are white families and the perpetrators are Pakistani Asians," the organisation's chair of trustees, Hilary Willmer, was quoted as saying. Sources inside Crop placed the percentage as high as 80 per cent, although Kurdish, Romanian and Albanian gangs were also involved.

But today Crop has become nervous about making public statements on the racial dimension of the abuse. "We've been accused of being a cover for the BNP," Ms Willmer told The Independent.

The girls whose families Crop tries to help aretypically targeted between the ages of 11 and 15. Accounts of their experiences still fill the organisation's website. Story after story shows how subtly and insidiously the grooming is done. Crop believes, based on limited reporting data, that as many as 10,000 children in the UK may be victims of sexual exploitation. But on the cultural background of the predators, Crop has gone suddenly silent. So too have the police.

Lancashire Police are so nervous about the subject that they would not even talk about a pilot project which is considered the national model for how to deal with the grooming of unsuspecting children. Called Engage, and based in Jack Straw's Blackburn constituency, it brings together a range of services – police, social workers, nurses, sexual health and drugs workers and Crop parents – to prevent, protect and prosecute.

The project carries out surveillance operations against men suspected of exploiting children sexually. It also issues legal warning notices to suspect adults and tours secondary schools with its own film, aimed at young teenaged girls and warning them – as Emma Jackson puts it – about the dangers they face "when they are 13 and so naïve and trusting about what can happen".

In the four years since it was formed Engage has rescued 80 children from sexual exploitation and got many back into school. It has had a conviction rate of 90 per cent. Working in the Eastern Division, which had the highest figures for missing children – and where only one offender had previously been convicted – the project uncovered, in 2008-2009 alone, a total of 100 offences of child abduction, rape and sexual activity with minors involving 36 individuals.

Strangely, however, Lancashire Police refused several requests over the past two months to talk to The Independent about the success of the project. So too did Nick McPartlan, the team manager at Engage. So did the project's parents' representative. All this hyper-sensitivity has led to accusations of political correctness from right-wing newspapers, whose anti-immigration agenda is neatly fed by suggestions that on-street grooming is a peculiarly Asian phenomenon.

"Police and social services have been accused of fuelling a culture of silence which has allowed hundreds of young white girls to be exploited by Asian men for sex," the Daily Mail has said. "Experts claim the statistics represent a mere fraction of a 'tidal wave' of offending in counties across the Midlands and the north of England which has been going on for more than a decade." It reported that one senior policeman, Detective Chief Inspector Alan Edwards of West Mercia Police, had called for "an end to the 'damaging taboo' connecting on-street grooming with race", quoting him as saying that "these girls are being passed around and used as meat".

The response of the Government was for the Children's minister, Tim Loughton, to warn that that "denial" over racial grooming did nothing to help victims.

"Political correctness and racial sensitivities have in the past been an issue," he said, and the authorities still "have to be aware of certain characteristics of various ethnic communities and be sensitive as to how we deal with them." All cases must be vigorously investigated, he insisted, though he added that grooming underage children for sex was not a problem exclusively associated with one particular community. So: what are those "certain characteristics of various ethnic communities"? And where does the truth lie?

Last year, the government's Child Exploitation and Online Protection Centre launched a five-month investigation into the issue. It took the broadest definition of underage grooming, describing it as any situation where a child or young person receives something in exchange for performing sexual favours.

The centre identified 2,379 potential offenders who had been reported for grooming since 2008. The vast majority were men. Most were aged 18 to 24. It could fully identify only 940 of the suspects. Of these, 38 per cent were white, 32 per cent were recorded as of unknown ethnicity, 26 per cent were Asian, 3 per cent were black and less than 1 per cent were Chinese.

These figures were reported in the media with various degrees of sensationalism. The 2001 census recorded 92.1 per cent of the general population as white, 2 per cent as black, 3.1 per cent as Indian or Pakistani, 1.2 per cent as "mixed" and 1.6 per cent as "other". But what was not prominently noted was that the centre's findings were heavily qualified by phrases such as "where ethnicity was recorded". What about the cases where it was not? The overall data was poorly recorded, inconsistent and incomplete, expert academics say.

"[The centre] drew data from a whole range of groups, like the children’s charity Barnardo’s, and as a result all the figures compiled have to be treated with caution as they were not all compiled in the same way," say Ella Cockbain and Helen Brayley from UCL. "There is no criminal offence of 'on-street grooming'. Consequently, it is very difficult to measure the extent of this crime based on court statistics," they say.

But the Child Exploitation and Online Protection Centre deliberately refrained from drawing conclusions about ethnicity, admitting itself that the data was "too inconsistent". "Focusing on this problem simply through the lens of ethnicity does not do it service," said its chief executive, Peter Davies. The organisation has passed the buck on this delicate issue to the government's Office of the Children's Commissioner, which is nine months into a two-year inquiry into child sexual exploitation by street gangs.

Until that inquiry reports, those who are reluctant to rush to racial stereotyping may, as Ella Cockbain puts it, "not be involved in a culture of silence so much as a culture of caution".

So what can we know about these victims and predators? Wendy Shepherd, child sexual exploitation project manager with Barnardo's in the north of England, says that most abusers are white and most child sex exploitation happens in the home. White males who are predators on the street tend to work alone, though they also prey in internet grooming rings, she says.

"When I started this work 12 years ago," she says, "the problem was mainly young people being put on the street by their older 'boyfriends'. An older man is anyone [who is at least] five years older than the girl. All ethnicities and professions were involved. Today it's much more hidden, with young girls being groomed at takeaways, in parks, shopping malls or bus stations.

"There has been a shift from the men selling children in ones or twos to something that is much more organised in groups and networks. The networks of men come from different backgrounds: in the North and Midlands many have been British Asians; in Devon it was white men; in Bath and Bristol, Afro-Caribbeans; in London, all ethnic mixes, whites, Iraqis, Kurds, Afghans, Somalis.

"The danger with saying that the problem is with one ethnicity is that then people will only be on the lookout for that group – and will risk missing other threats." The gifts given to girls in grooming are breathtakingly trivial. Often the presents involved are nothing more than a bag of chips, a cigarette or two, or a few illicit swigs of vodka. "Gifts such as mobile telephones are far less common," say Ella Cockbain and Helen Brayley. Attention, affection and excitement are often enough.

And for all the talk about "gangs" of offenders, the two researchers from UCL's Jill Dando Institute of Security and Crime Science say a lot of grooming has little to do with organised crime. "The offenders abused their victims casually, almost as a hobby-type behaviour," they say. "While some cases have involved the commercial exploitation of victims this is not the norm. When victims have been sold for sex this has typically been at prices below the market rate."

The big problem that the police have in prosecuting over these offences is that many of the abused girls do not see themselves as victims. When questioned by the police they continue to describe their abusers as their "boyfriends". In the case that ended at Liverpool Crown Court on Tuesday, one of the teenage girls, who was made pregnant by her abuser, had said earlier, under cross-examination, that she was still in love with him.

Such attitudes are commonplace. Child sex abuse can involve brutal and savage behaviour, but most instances, according to the UCL researchers, the abusers are coercive in more subtle ways, using confusion, peer pressure and emotional blackmail as well as alcohol and drugs.

"Grooming is best understood as a cumulative process: the way a victim is treated by one offender may affect their response to another," say Cockbain and Brayley. Girls can draw their friends into the offending groups, sometimes to feel safety in numbers, though sometimes to distract an abuser. "You are dealing with teenagers," says Cockbain, "and most teenagers do stupid things. It is just that generally those stupid acts do not lead them into serious danger." That explains why Crop, the support group for the parents of sexually exploited girls, is so keen to emphasise that victims are not just dysfunctional kids from broken homes or children in local authority care – though most victims are – but can also be middle-class girls who have ponies.

"It can happen to any child in any family," says Hilary Willmer, Crop's chair of trustees. Indeed, girls from more sheltered backgrounds, who are less streetwise, may be easier targets. "Affected families come from right across the social spectrum. What they have in common is that their child has been 'caught' by clever manipulative criminals who know exactly what they are doing. Part of the grooming involves alienating the child from her family. Parents are bewildered, angry, and feel guilty but they are then often judged and blamed as well for what has happened. The whole family become victims."

What cannot be denied in all this is that – whether the percentages are disproportionate or not – significant numbers of British Pakistani men are involved in such abuse. The Child Exploitation and Online Protection Centre report hinted at that when it said that many offender groups "were related to each other in some way, either as friends, family members or work colleagues" – noting that "where offenders worked together, the place of work was either a takeaway restaurant or a taxi firm".

Martin Narey was the director-general of Britain's prisons for seven years, after which he became chief executive of Barnardo's, the charity which cares for vulnerable children and young people. "When I began at Barnardo's I was resistant to the idea that there was a racial or cultural dimension to child abuse," he says. "If anything, my experience in running the Prison Service taught me that sex offenders were generally white. But some time ago I decided that in not exploring that we were leaving children at risk. I found the picture not to be constant, but certainly in the North the repetitive evidence of Asian men as perpetrators could not be ignored."

This is not to buy into the British National Party's "Our Children are Not Halal Meat" anti-Muslim agenda. The BNP refers to this type of offending as "Muslim paedophilia", but, as Ella Cockbain and Helen Brayley point out: "This is misguided for two reasons. First, it is not paedophilia since the victims are not pre-pubescent.

"There is also no indication that the offenders are exclusively or preferentially sexually attracted to minors. Secondly, religion seems to be a red herring here, in that many offenders seem to be Muslim only in a nominal sense. Prior to arrest many drank alcohol, took drugs, did not have beards, and all engaged in extramarital sex with underage girls. Hardly the hallmarks of a strict Muslim."

The evidence that the Jill Dando Institute of Security and Crime Science has gathered suggests that victims are targeted not because they are white but rather in a haphazard opportunistic manner – with the perpetrators cruising the streets for whatever girls they happen to see hanging about there. Convenience and accessibility, rather than race, appear to be the primary drivers. The men go for the easiest targets.

"Indeed, though most of the victims are white British," the researchers say, "the proportion of black and minority ethnicity victims was actually higher than what might be expected, given the local demographics." Martin Narey agrees. "I have never subscribed to the view that these men have some sort of moral code and would not abuse Asian girls," he says. "They'd abuse any child over whom they could exert power. The reality, however, is that the girls who make themselves vulnerable on our cities, particularly at night, are generally white. Asian girls, more strictly parented, are at home."

Even so, it is clear that some Asian men do target underage schoolgirls and attempt to groom them for sex. The exact proportion may be unclear because the statistics on these crimes are so incomplete and inconsistent. But there is a serious problem within parts of the British Pakistani community.

What is to be done about that? Wendy Shepherd, Barnardo's on-street grooming expert is clear. "As with any community where child sexual exploitation is occurring," she says, "you need to engage the community and its leaders to combat the problem".