A government minister has warned that inbreeding among immigrants is causing a surge in birth defects - comments likely to spark a new row over the place of Muslims in British society.

Phil Woolas, an environment minister, said the culture of arranged marriages between first cousins was the “elephant in the room”. Woolas, a former race relations minister, said: “If you have a child with your cousin the likelihood is there’ll be a genetic problem.”

The minister, whose views were supported by medical experts this weekend, said: “The issue we need to debate is first cousin marriages, whereby a lot of arranged marriages are with first cousins, and that produces lots of genetic problems in terms of disability [in children].”

Woolas emphasised the practice did not extend to all Muslim communities but was confined mainly to families originating from rural Pakistan. However, up to half of all marriages within these communities are estimated to involve first cousins.

Medical research suggests that while British Pakistanis are responsible for 3% of all births, they account for one in three British children born with genetic illnesses.

The minister’s comments come as Rowan Williams, the Archbishop of Canterbury, rejected calls to resign over claims that Islamic law should be introduced in Britain. “I’m not contemplating resignation,” he told friends.

Williams insists his remarks were misinterpreted and that he was not advocating a parallel sharia jurisdiction for Muslims, but Lord Carey, his predecessor, warned acceptance of Muslim laws in Britain would be "disastrous".

The archbishop is believed to have received hate mail since he made his controversial comments but has rejected offers of round-the-clock police protection.

Williams is set to clash with the government again this week by voicing opposition to plans to extend detention without charge for terrorist suspects to 42 days.

Woolas, who represents the ethnically mixed seat of Oldham East and Saddleworth, has previously warned that Muslim women who wear headscarves could provoke “fear and resentment”. Yesterday, he was similarly outspoken.

“If you talk to any primary care worker they will tell you that levels of disability among the . . . Pakistani population are higher than the general population. And everybody knows it’s caused by first cousin marriage.

“That’s a cultural thing rather than a religious thing. It is not illegal in this country.

“The problem is that many of the parents themselves and many of the public spokespeople are themselves products of first cousin marriages. It’s very difficult for people to say ‘you can’t do that’ because it’s a very sensitive, human thing.”

He added that the issue is not talked about. “The health authorities look into it. Most health workers and primary care trusts in areas like mine are very aware of it. But it’s a very sensitive issue. That’s why it’s not even a debate and people outside of these areas don’t really know it exists.”

Woolas was supported by Ann Cryer, Labour MP for Keighley, who called for the NHS to do more to warn parents of the dangers of inbreeding.

“This is to do with a medieval culture where you keep wealth within the family,” she said.

“If you go into a paediatric ward in Bradford or Keighley you will find more than half of the kids there are from the Asian community. Since Asians only represent 20%-30% of the population, you can see that they are over represented.

“I have encountered cases of blindness and deafness. There was one poor girl who had to have an oxygen tank on her back and breathe from a hole in the front of her neck.

“The parents were warned they should not have any more children. But when the husband returned again from Pakistan, within months they had another child with exactly the same condition.”

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