The compound was found to destroy such viruses and bacteria when dissolved in a gel.

It also shows potential as a contraceptive, as it can halt the movement of sperm.

The fat, called monocaprin, is commonly found in foodstuffs.

Once dissolved in a gel, it was able to destroy HIV, herpes viruses and the bacteria that cause gonorrhoea within a minute.

It took five minutes to destroy chlamydia - the sexually-transmitted bacteria linked to infertility.

And it decimated the number of white cells in semen, which are thought to play a key role in the sexual transmission of HIV.

Experimental studies

Dr Halldor Thormar, a virologist at the University of Iceland in Reykjavik, reported his research in the journal Sexually Transmitted Infections.

The gel also reduced the movement of sperm

He stressed that the work was still in the experimental stages and results had so far been limited to laboratory tests.

However, the fat could prove extremely useful in preventing the transmission of sexually-transmitted infections.

"It has the potential to be used either as a preventative measure or as a treatment of certain important viral and bacterial infections," he said.

Other substances have been shown to kill off such bacteria and viruses, but when used regularly by animals, they have turned out to be toxic.

But much of monocaprin's potential lay in the fact that it was a substance with which the body was already familiar, Dr Thormar said.

The next stage was to test how the gel performed on animals, he said.