A new male ‘pill that is hormone free and can be taken hours before sex could usher in a revolution in male contraception.
This would make it much more acceptable to men than other 'male pills' under development, which alter hormone levels and have to be taken over the long term.
The hormone-free 'male pill' was inspired by two medicines already in use and so the scientists hope it could be on the market within as little as five years.
Experts believe it could transform family planning by allowing couples to share the responsibility for contraception - a role that traditionally falls to women.
The new contraceptive is likely to appeal to women who are uneasy about the female Pill's ability to raise the risk of strokes, heart attacks and potentially-fatal blood clots.
Critics argue, that men lack women's motivation to prevent pregnancy, making it hard for women to trust them to take a contraceptive pill.
Other male pills are under development but many of them are based on hormones that trick the brain into switching off sperm production. These are typically being developed as injections, implants and patches.
However the new pill being researched by scientists at King's College London, contains chemicals that prevent ejaculation and could be in tablet-form.
Men could take one daily, just like the female pill, or have one a few hours before sex as a one-off contraceptive.
Sexual satisfaction is not affected and the absence of hormones means that a man's fertility should return to normal within hours of stopping the treatment.
"The non-hormonal male pill could be taken when and as needed," researcher Dr Nnaemeka Amobi was quoted by the Daily Mail, as saying.
"If the man was taking the pill over a period of several months and decided to come off it, we would expect his fertility to return just as quickly as if he had taken it on a one-off basis," fellow researcher Dr Christopher Smith added.
The contraceptive was inspired by the observation that some drugs used to treat schizophrenia and high blood pressure also prevent ejaculation. However, side-effects including dizziness and drowsiness mean these medicines could not be marketed as contraceptives.
Professor John Guillebaud, one of Britain's leading experts on contraception, described the pill as "a brilliant discovery".
He said its strength lay in its ability to prevent pregnancy without using hormones which could cause side-effects such as hot flushes and moodiness.