More than a quarter of women have had an unplanned pregnancy and nearly half were because of problems with contraception, according to a poll of more than 5,000 women.

The results were released yesterday to mark the UK launch of a new contraceptive patch, Evra (pictured).

The weekly patch delivers continuous levels of hormones through the skin into the bloodstream.

It is already available in the US, where it has become the second most widely prescribed hormonal contraceptive in less than 12 months.

Family planning groups in the UK welcomed the new patch, saying it should help cut the numbers of unwanted pregnancies, because women would not have to remember to take a daily Pill but simply change the patch once a week.