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

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 Sunday.

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