The team now plans to test the chemicals in animal and human studies and hopes to have a treatment in five years.

Fertility experts welcomed the work, saying it could mean couples could share contraceptive responsibility.

Several other male contraceptives, given as injections, implants or patches are under development. Most are based on hormones which trick the brain into switching off hormone production.

The treatment being developed at King’s acts by preventing the longitudinal muscle in the vas deferens contracting to propel sperm out of the penis.

The drugs, designed to treat schizophrenia and high blood pressure and stopped men ejaculating, were found to have this effect over a decade ago.

But they have side effects such as dizziness and drowsiness, which meant they could not be used as contraceptives. Tests on human tissue have helped identify chemicals which have the same effect.

The team is now set to test the treatment on animals and then humans. It is proposed men would take a pill each day, as women do with the female contraceptive pill, or could take one a few hours before they plan to have sex.

Because the contraceptive is not dependent on hormones, the researchers suggest a man’s fertility should return the following day.