Tough new controls on in-vitro fertilisation (IVF) must be introduced to cut the soaring number of twins being born, a report says.

Healthy younger women having fertility treatment should have only one embryo replaced in their womb at a time, instead of the present maximum of two, to reduce the risks in multiple births, says the study by fertility experts, for the Human Fertilisation and Embryology Authority.

And, in a swipe at the Government, the team says the failure of NHS trusts to provide three cycles of IVF treatment for each infertile woman, as recommended by the National Institute for Clinical Excellence (Nice) in 2004, is "the single greatest obstacle" to introducing replacement of one embryo at a time in the UK.

Twin births have risen by 66 per cent in Britain from 6,000 a year in 1975 to almost 10,000 a year, driven by the increase in IVF. One in four IVF pregnancies leads to the birth of twins compared with one in 80 natural conceptions.

But a twin pregnancy is risky. Professor Peter Braude, chairman of the expert group and a fertility specialist at St Thomas's Hospital, said many couples saw twins as a way of acquiring an instant family without recognising the dangers. The chance of complications in the mother of twins increased sixfold, and the risk of death of the babies in the first month of life by sevenfold.

"Multiple birth is the single biggest risk to the health and welfare of children born after IVF," he said. "We can no longer sit back and do nothing. IVF children also deserve the best start in life."

For the past 25 years, since IVF began, specialists have routinely replaced more than one embryo to increase pregnancy rates. IVF is physically and emotionally draining and most women are anxious to get it over with quickly. Private treatment costs about £3,000 per cycle and some women have a dozen cycles.

In the early days, specialists replaced up to a dozen embryos at a time and some women gave birth to quads, quintuplets and sextuplets.