Superdrug, the high street chemist, yesterday added the morning-after pill to the bunion pads and headache tablets available on its website, becoming the first retailer to sell emergency contraception over the internet.

Priced at £19.99 for a pack of two pills, the product will only be available in the London area bordered by the the M25 motorway. Customers will be charged a further £7.50 for an express four hour delivery. To be effective, the pills must be taken within 72 hours.

The superdrug.com service takes advantage of a change in law which came into effect on January 1 removing the drug Levonelle from prescription-only control and permitting women to buy it over the counter. There is no charge for the drug when it is prescribed by a GP or family planning clinic.

While the Family Planning Association welcomed the initiative as a sensible way of giving women access to emergency birth control, the anti-abortion group Life raised concerns that it could be exploited by under-age customers and encourage promiscuity. This week, it emerged that two underage boys from West Sussex were sold Levonelle over the counter after claiming to have had unprotected sex with fictitious girlfriends. "This service will be open to abuse, with people getting the pill for other people and underage girls," a spokesman for Life said.

Superdrug pointed to its strict purchasing procedure. Women will register on the website and be called back by a web pharmacist, who will take them through a series of questions set out in the Royal Pharmaceutical Society's guidelines. These include the chemist's duty to satisfy himself that the client is 16 or over, is buying the drug for her own consumption and is not allergic to levonorgestrel, an ingredient in Levonelle.

In what Superdrug identified as a further filter for the underage, customers will be asked to pay by credit or debit card. After the pharmacist has approved the sale, women will either order an express delivery or go to their nearest chemist to pick up the pill.

Barry Simner, head pharmacist at superdrug.com, said: "We can help people with their planned contraception methods and the availability of Levonelle allows us to help people who need emergency contraception."

Juliet Hillier, of the Family Planning Association, said: "If a pharmacist calls you back to discuss your order, it's not an anonymous service open to abuse. It looks like a very innovative approach to ensure that women have access to emergency contraception."

Ann Furedi, of the British Pregnancy Advisory Service, said: "We think it is a great initiative and welcome it hugely."