When it comes to sex, Alyas Karmani is a plain-speaking man. For a Muslim imam he is breathtakingly so. "Oral sex and anal sex are taboo in the British Pakistani community," he announces matter-of-fact way over gosht palak in his favourite curry-house just up the hill from Bradford University. "Sex is seen as only for procreation and only in the missionary position. More so if your spouse is from abroad."

He is addressing the question of whether a disproportionate number of British Asian men are involved in grooming underage girls for sex. He thinks the answer is "Yes" – which is also very plain-speaking on a subject around which the British policing, political, academic and social work establishment dances with over-sensitive diplomacy.

Yet Imam Karmani is no maverick. As well as being an imam, he is a psychologist with more than 20 years of practical experience in youth and community work. He is a former adviser to the Department for Education on youth empowerment and a one-time head of race equality for the Welsh Assembly and is now co-director of Street, a project whose name stands for Strategy to Reach, Empower and Educate Teenagers.

One of its key projects is running courses to change the attitude of young British Pakistanis which, Alyas Karmani believes, underlie the cultural assumptions which have led a number of Asians to become involved in the on-street grooming of schoolgirls for sex. Eight men of Pakistani heritage, and an Afghan, were were convicted at Liverpool Crown Court this week of offences including four rapes, 11 charges of conspiracy to engage children in sexual activity and six of trafficking children for sexual exploitation.

"Many British Pakistani men live in two worlds," he begins. "The first is encompassed by family, business, mosque. It is a socially conservative culture where there is no toleration of sex outside of marriage, and little emphasis on sexual gratification."

Many are emotionally browbeaten into preserving their family honour by marrying a cousin from their family's village in north-west Kashmir, the part of Pakistan from which the forefathers of Bradford's Asian community originally migrated.

These new wives can bring with them "an unhealthy attitude towards sex and sexuality". It is not Islam which induces that, he says, but a traditional rural Kashmiri culture.

"The second world in which British Pakistani men live," he continues, "is the over-sexualised, material and lust-driven English lifestyle, where women are scantily clad, binge-drinking is a mainstream form of entertainment and porn is a massive factor." You might have thought that, as time passed, British Asians would have found middle ground between these two worlds.

But that has not been happening. "Patriarchs and matriarchs within families have huge influence," says the imam. "Conservatism is maintaining its grip. Around 60 to 70 per cent of British Asians, men and women, are still virgins when they marry."

For those Asians who work at night –such as taxi-drivers and takeaway workers – these two worlds collide dramatically in their workplaces which are filled with young women from a culture in which drinking to insensibility is commonplace. "Many of these men do not understand what is appropriate behaviour in wider society and what is not," he adds. "They are so lacking in social skills – because relationships between men and women in Pakistani culture are characterised by a real formality – that they can misconstrue an ordinary conversation with a white girl in their taxi and think she is indicating that she is open to a sexual advance when that is not what she means at all."

Others cannot resist the temptation aroused by women – and young girls – whose cultural assumptions are so alien from their own.

There are a number of ways, says Alyas Karmani, in which second and third generation British Pakistani men cope with the cognitive dissonance induced by living with two conflicting cultures.

Some give in to the temptations of Western life – which in an Asian urban context might mean celebrating values embodied in gangsta music and films. "It links sexual violence with gang lifestyle and glorifies it through rap and videos which degrade a man to 'pimp' and a woman to 'bitch'," Karmani says. Others turn their back on that and embrace religion, sometimes in a puritan or even jihadist way. But many are conflicted into living a double life.

They do that in a variety of ways. "Some have a wife from Pakistan and an English girlfriend by whom they may also have children," he says. "In some cases the English girlfriend predates the wife; some relationships go back to schooldays. Sometimes the arrangement is open – the wife knows about the other family but says nothing. Sometimes even the man will marry the girlfriend under Islamic law, though not under British law, obviously. Some of these relationships are exploitative, others are consensual.

"Some of these men with double lives, who lack the social skills to go out and chat up a white girl of their own age, use prostitutes for sexual gratification," he continues. "But a few abuse the sexuality of vulnerable young girls they come across as taxi-drivers and in takeaways. It's important to stress that this grooming behaviour is not an endemic pattern among Pakistani men; overall there is only a very a small minority of Pakistani men involved in grooming and sex gangs."

Some in the Asian communities resent even this very qualified criticism. Iftikhar Ahmad, of the London School of Islamics Trust, has complained that "native Brits have double standards and are hypocrites [who] don't mention the fact that the majority of men who go to countries in east Asia looking for under-aged sex are white European men".

But generally condemnation from religious and community leaders in the Asian community has been slowly growing over the past two years as a succession of cases has reached the courts in which men from the Asian community have been convicted of crimes involving the sexual exploitation of underage girls.

Expressions of shame, however, have outnumbered attempts at analysing whether there are specific qualities in ethnic minority culture which nurture the attitudes from which abuse springs.

Six years ago, Mohammed Shafiq, who runs the Ramadhan Foundation, a small Muslim youth organisation in Manchester, spoke out about the involvement of British Pakistanis in underage sex abuse crimes. He was roundly vilified by his own community. "I was accused of doing the work of the BNP," he recalls. "I had excrement through my door. I received death threats." His offence was to insist that "to say that ethnicity is not a factor in these crimes is a lie".

Members of Asian grooming gangs, he said, thought "that white girls are less valuable than girls from their own community, which is sick and abhorrent". This grew, he declared, from an assumption among some members of the Muslim community that "white girls have fewer morals".

More recently, up the road from Bradford in Keighley, a youth worker named Shakeel Aziz has spoken out, declaring sexual grooming to be "an extension of other criminal activity, specifically gang association and drug selling. It's really a jigsaw of different problems and issues in society that enforce one another," he said. And last year the broadcaster Adil Ray, a DJ and comedian with the BBC Asian network, set out another hypothesis in a BBC Three investigation into on-street grooming. He asked whether there was something particular about the Kashmiri culture that nurtured abusive attitudes.

Ray, who is from a Pakistani community in Birmingham, interviewed Yasmin Qureshi, the former specialist sexual offences lawyer who is now MP for Bolton South East. He noted that most of the cases of grooming by Asians occurred in the North and Midlands, which is where in the main immigrants from Kashmir settled to work in the factories and mills. The MP concurred. "In the south... there's more integration between communities," she said. "You very rarely find a school that has 80 per cent of one nationality. The people who came and settled in the south came from a much more educated, literate background... You can't take away from the fact that a lot of people come from Kashmir where some of the communities are culturally quite traditional."

This is not so far from the claim made in 2003 by Ann Cryer, then Labour MP for Keighley, that Pakistani men were exploiting local children because they had married, or been promised in marriage, "to someone they've never met, some cousin from their village in Mirpur who is almost certainly illiterate and hasn't got anything in common with them".

Alyas Karmani agrees with Mohammed Shafiq about the dissonance caused for British Pakistanis caught between two cultures. And he agrees with Shakeel Aziz that there can be an interplay between grooming and drug and gang cultures. But he does not accept the idea that Kashmiri culture is somehow more backward and thereby to blame.

"That's a flawed analysis. It's not about education. It's about access and opportunity," he says. "These men – and it's worth stressing that only a very tiny minority have deviated in this way – are not targeting white girls specifically but going for those who are most easily accessible and vulnerable, and that is by definition mainly white girls as young Asian teenagers are within the protection of the home at that time of night.

"The issues around ethnicity and sexuality are complex," he continues. "Some powerful gangsta types have white girlfriends as status symbols. They would not dream of sharing them with anyone.

"But other 'big men' think it adds to their status and kudos if they pass their conquests around to their 'brothers' under biradiri – the system of clan loyalty which has been brought here from Kashmir. That is often the case with those who abuse young girls. They involve brothers or cousins or friends from their clan."

That observation is confirmed by academic researchers working on child sex exploitation. Analysis by Ella Cockbain and Helen Brayley at University College, London's Jill Dando Institute of Security and Crime Science shows that abusers' networks were "tightly knit and characterised by strong social bonds predating the abuse, such as kinship".

Gangs did not develop around a shared furtive interest in child sex abuse. Rather, abuse was introduced into pre-existing social networks.

"Sometimes money changes hands," says Imam Karmani. "But not large amounts. Most of the girls are enticed into relationships with the smallest of gifts – a £5 top-up for their mobile phone, a free kebab or bag of chips. Any girl who is unprotected can be targeted. It's not racist; it's opportunistic. They are usually girls from damaged or dysfunctional backgrounds, who are out on the streets at all hours."

So it is not about race, he insists, though it grows out of cultural presuppositions. "These men disrespect all women, but these white girls are more vulnerable. They objectify women, just as white footballer rapists do," he says. "Porn," he adds, "plays a big part in it."

What can be done about all this? Wendy Shepherd, of the children's charity Barnardo's, is one of the UK's most experienced on-the-ground experts on child sexual exploitation. She has a checklist of necessary improvements. It coincides almost entirely with that of Ella Cockbain and Helen Brayley from the Institute of Security and Crime Science.

The improvements include better police training and strategies, so that prosecutions do not simply fail because there is no evidence beyond the word of the victim against the abuser; greater co-operation and information sharing between police, social workers, doctors, nurses, teachers and charities; more direct help for victims, including those who don't know they are being abused; and more work with children in schools to raise awareness of the risk.

But vital to the list, says Wendy Shepherd, is that the younger generation of men needs to be educated in better attitudes towards women.

That is precisely what Alyas Karmani has begun to do. All across the country – but mainly in Bradford, Blackburn, Manchester and London – he runs courses aimed at three key groups. "We run From Boys to Men courses for 11- to 13-year-olds to talk openly about puberty, bodily changes, sexual attraction and Islamic teaching on there being no sex before marriage," he explains. "Many have had no conversation with their fathers, because sex is an embarrassing and even shameful activity in traditional Pakistani culture.

"Sex education in schools does not address real life issues and challenges," Karmani adds – and a lot of the boys had been removed from sex education classes at school on religious grounds. "So all their information is from their peers, the streets or the internet. They have no understanding of sex in a loving relationship, or any understanding of what is permitted and forbidden in Islam. They confuse Islam with conservative Pakistani culture."

He runs run similar courses for 14-to 19-year-olds, which also deal with drugs, alcohol, gangs and violence. "Many of these kids just want an adult male to talk frankly with them. They have to learn the importance of self-respect and not being susceptible to peer pressure or older men who offer them alcohol or want to take them to the brothel. Teaching respect for themselves and respect for women is part of that. The sessions also deal with social networking and internet, violence and sex, honour killings and domestic violence, sex offending, grooming, statutory rape, "date rape" and indecent assault.

"We talk about what is abusive and what not – and about the need to respect white women and the damage that on-street grooming does to the victim, the man and the wider community," he says.

"We look at famous case histories, like Britain's youngest rapist, who was 13. We don't flinch from hard cases and will answer any questions whatsoever. And we do some hard-hitting aversion therapy using the filmed testimony of women who have been raped – who are someone's daughter and sister."

For adults, he runs a "Joy of Muslim Sex" course. "I talk to the men and my wife talks to the women," he explains. "What you have to understand is that these people are coming from a Pakistani culture in which no demonstration of affection is allowed between a married couple in public or in front of their children – not even a peck on the cheek or holding hands.

"That would be completely shameful behaviour. We try to teach them to overcome that and to be affectionate with one another, to create time and space. That's hard in a community where it's common for two brothers and their wives to live with the men's parents still.

"We talk about pre-play and foreplay, about the importance of hiring a hotel room once in a while for private space for prolonged pleasure, getting to know one another better. Sometimes the women, especially those who have come from Pakistan for an arranged marriage, need lessons on how to seduce their husbands. I told one woman that she needed to pay more attention to her husband and she paused and said: "I'll iron more of his shirts then". I had to explain that wasn't quite what I meant."

The course uses material from the 15th-century erotic Arabic sex manual The Perfumed Garden. "The men need to be told that sex for women is about emotional intensity more than the mere physical. The demand for all of these courses is huge," he concludes. "I could spend all my time doing nothing else. The need is massive."

Men like Alyas Karmani are trying to get the British Asian community to address a problem from which, he admits, it has been in denial. But it is not enough simply to point the finger at Asians, as Wendy Shepherd points out. Her long experience with Barnardo's shows that if you scratch the surface you'll find some pretty appalling attitudes towards women in the white community too.

"It's not that long ago that a man could get drunk on a Sunday lunchtime and go home and give his wife a beating and people would accept that as normal," Wendy Shepherd says. "The danger with saying that the problem is with one ethnicity is that then people will only be on the look-out for that group – and risk missing other threats."