The 40-foot contraceptive is part of "The Safest Ad in the World?" unveiled alongside the Kennington Road, Lambeth, South London, on Monday.

The advert is designed to promote the safe sex message ahead of World Aids Day on Tuesday.

The Terrence Higgins Trust, an HIV charity, fears that because drugs such as AZT have enabled successful treatment of Aids symptoms, people have become complacent about the disease.

However, a cure for the disease is still years away, and despite a decade-long campaign to cut infection through educational programmes, the number of Aids cases worldwide increased by 10% this year. In total 33.4 million people are infected by the virus around the globe.

Claire McMaster, of the Terrence Higgins Trust, said: "We want to make sure people remember World Aids Day - and anyone who sees this poster is unlikely to forget!

"There is absolutely no room for complacency with HIV/Aids. We hope this billboard will remind people of the importance of practising safer sex."