A contraceptive patch providing nearly 100 per cent effective birth control could be available in Britain next year after it was given approval to launch in America on Tuesday.

The Ortho Evra patch works like nicotine patches to release the same hormones as the contraceptive pill but eliminates the risks of women forgetting to take the pill.

It was approved by the US Food and Drug Administration yesterday after years of trials in a decision that could revolutionise the contraceptive routine of millions of women.

Last night, the Family Planning Association said the move was "great news" for women as it would provide a new choice of contraceptive that could cut the number of unplanned pregnancies. It said the patch was "on schedule" to be approved in Britain next year.

Produced by Johnson & Johnson's subsidiary Ortho-McNeil Pharmaceutical Inc, the patch is 99 per cent effective, like the pill, and can be worn for a week at a time attached to the arm, upper body, buttocks or abdomen. Women would wear the one-and-three-quarter-inch square patches for three weeks and then have a fourth "patch-free" week during their menstrual period.

It was approved after trials to test whether it remained attached and effective during bathing, swimming and exercising or while worn in humid conditions. About 5 per cent of women had at least one patch that did not stay attached and needed to be replaced.

Dr Patricia Stephenson, one of the medical staff involved in the clinical trials, said: "Although there are a variety of birth control methods to choose from, many women still desire new options. Ortho Evra offers ... a highly effective method of birth control that is simple and easy to use."

Dr Dena Hixon, an FDA medical officer, said the patches appeared to be less effective in women weighing more than 198lb (90kg) because a third of pregnancies in the trials were in women of that weight range. Such women should discuss using the patch with their doctors, she said.

The patches do have safety risks, similar to birth control pills, that include a higher risk of blood clots, heart attacks, and strokes. They will carry a standard warning for hormonal contraceptives that cigarette smoking increases the risks of serious side-effects.

Anne Weyman, chief executive of the Family Planning Association, said the patch was on schedule for launch in Britain next year, assuming it was approved by the Medicines Control Agency.

She said: "If it has got approval in the US it is a great step forward and great news for women because it increases their contraceptive choices.

"It is quite safe when you go swimming as they stick to the skin and many women will find it an acceptable method. It will end the need to have to remember to take a pill every day so the number of unplanned pregnancies should be fewer."

The Department of Health said the patches would have to go through the normal regulatory bodies and no decision was imminent on licensing them in Britain.

A spokeswoman for Johnson & Johnson said the company had applied for approval in Europe and could not speculate on when the patches might be available in Britain.