London - Hundreds of Britons are being urged to attend what is being branded as Europe's first "Masturbate-a-thon", a leading reproductive healthcare charity said on Friday.

Marie Stopes International, which is hosting the event with HIV/ AIDS charity the Terrence Higgins Trust, said it expected up to 200 people to attend the sponsored masturbation session in Clerkenwell, central London, on Saturday.

"It is a bit of a publicity stunt but we hope it will raise awareness," a Marie Stopes spokeswoman told Reuters.

"We want to get people talking about safer sex, masturbation and to lift taboos."

Participants, who have to be over 18, can bring any aids they need and can take part in four different rooms -- a comfort area, a mixed area, along with men and women only areas.

However, the rules on the event's Web site states there can be no touching of other participants nor are people allowed to fake orgasms.

"The amount you raise will be determined by how many minutes you masturbate and/or how many orgasms you achieve," the Web site said.

The Marie Stopes spokeswoman said local religious groups had been initially outraged, but after people had heard what the event was about, most had approved it.

Police had also given it their approval.

Similar events have been staged in San Francisco for the last six years raising $25,000 (13,000 pounds) for women's health initiatives and HIV prevention. If successful, Marie Stopes said it could take place elsewhere in mainland Europe next year.