The number of women buying the morning-after pill from chemists has nearly doubled in a year, figures show.
It is only effective within 72 hours of unprotected sex
Over-the-counter purchases rose from 27% in 2003/04 to 50% in 2004/05, the Office for National Statistics found.
Fewer women asked their GP for a prescription for the emergency contraceptive in the same time period.
However, the percentage of women using it remained the same - about 7% of women aged 16-49 using the morning after pill every year.
Chemists have been allowed to sell the morning-after pill without a GP prescription since 2001.
The proportion of women obtaining the morning-after pill from their own GP or practice nurse fell from 41% in 2003/04 to 33% in 2004/05 but the proportion getting it from a family planning clinic remained stable at 21%.
Condom failure was the reason for needing emergency contraception given by over two fifths (46%) of women.
The most popular method of contraception remains the pill, with a quarter of women aged 16-49 relying on it.
The second most popular method was the male condom, used by 22% of the women studied.
About 6% of women used the morning after pill once during 2004/5, 1% used it twice and less than 1% used it more than twice.
Toni Belfield, of the Family Planning Association, said: "It is understandable that women will find their local pharmacy an easier place to get hold of emergency pills, because of longer opening hours and greater accessibility.
"This is important because emergency hormonal contraception is only effective within 72 hours of unprotected sex so the sooner women get hold of it the better."
She said it was important that women be made aware that they could also obtain it free from their GP or Family Planning Clinic.
She added that sexually active people should also be alert to the risk of sexually transmitted infections and practise safe sex.
David Pruce, of the Royal Pharmaceutical Society of Great Britain, said: "We are issuing thousands of leaflets over the next few weeks through pharmacies to highlight the importance of safe sex and explaining how people can get help for sexually transmitted illnesses."
A spokesman from the Society for the Protection of Unborn Children said women should be aware that emergency contraception could cause what he termed abortion because it can stop a fertilised egg from implanting as well as working by stopping an egg being released in some women.
"For that reason we oppose its use. We are against the destruction of unborn children.
"We also oppose greater and easier access and availability to such powerful drugs, which we fear is happening.
"They are so freely available they are seen as a safety net for contraceptive failure."