One in five young women used the morning-after pill last year, causing experts to warn them that they are putting their health at risk.
And a quarter of a million women have used the drug three times or more.
The figures are based on a poll of 3,000 people by The Co-operative Pharmacy on sexual behaviour trends over the past twelve months.
The morning-after pill contains a powerful dose of hormones, which can act to abort an embryo.
Infections
The survey also revealed that chlamydia is the most common sexually transmitted disease, followed by genital herpes and gonorrhoea.
A sixth of women who took part in the survey admitted having had a sexually transmitted infection.
And according to the Health Protection Agency, almost half a million new infection cases are diagnosed in the UK each year.
Risks
The survey has caused concern to Mandeep Mudhar, Head of NHS development at The Co-operative Pharmacy.
“Our research shows that some women are taking unnecessary risks with their health”, he said.
He added: “The emergency contraceptive pill does not protect against sexually transmitted infections”.
Warnings
The statistics come after warnings last year from family values groups about the dangers of the morning-after pill.
Norman Wells, of campaign group Family Education Trust, said: “The easy availability of the morning-after pill has a damaging social effect, by lulling young people in particular into a false sense of security, encouraging a more casual attitude to sex, and exposing them to increased risk of sexually transmitted infections.”
And Josephine Quintavalle of Pro-Life Alliance said: “This is not a contraceptive, it is an abortive agent.”