A veteran MP has called for a ban on cousin-marriage - practised by South Asian Muslims - in Britain, claiming it is leading to a striking rise in the incidence of rare recessive disorders, many of them fatal.

"We give warnings about the dangers of smoking, drinking and taking drugs. It is now time that primary care trusts started doing the same for cousin marriages," said Anne Cryer, an MP from the ruling Labour party and a leading British campaigner on social issues.

Cryer's potentially controversial call comes ahead of a major debate to be held by the Royal Society of Medicine later this month to mark 100 years of medical genetics.

Cryer said she had Asian constituents whose children were severely disabled.

"In our local school for deaf children, half the pupils are of Asian origin though Asians form about 20 percent of the population" in her constituency of Keighley in Bradford, a northern England city with a large Pakistani population from the region of Mirpur.

"I also know of several sets of parents in my constituency who are cousins and whose children are severely disabled. I have no doubt that the mothers and fathers being closely related to each other is a key factor," she added.

Although there is anecdotal evidence of the kind contained in Cryer's comments - reported in the Observer newspaper Sunday - the extent of the practise is not clear.

Nor is it entirely clear if this debate is being framed around nationality, religious or cultural lines, or whether it is being addressed as a purely health issue.

In Britain, not only Pakistanis practise cousin-marriage, but there is also some evidence of marriages between cousins from India.

Some doctors also dispute the claim - made earlier this year by Environment Minister Phil Woolas - that cousin-marriage could lead to "a genetic problem."

Defending the practise, Aamra Darr, a senior researcher at Bradford University, said there are no calls for banning Britons over the age of 30 from giving birth, although with more and more women marrying after the age of 30 there was a likelihood of an increase in the number of Down's Syndrome babies in Britain.

The debate over cousin-marriage is quite separate to the nation-wide campaign against forced marriage, where first generation South Asians force their children to marry partners from their country of origin, often with threats and actual physical violence.