In the course of two year trials, at 15 centres around the world, the contraceptive was tested on more than 400 men and it has been shown it to be as effective as the pill for women, and safer than using a condom.
The British doctor on the research team, Dr Fred Wu, a senior lecturer at Manchester University, described it as a "breakthrough" for the male contraceptive. He said: "It is very significant. It is really showing the world for the first time that permanent contraception for men really works."
For the men testing the contraceptive the only drawback is the form it comes in, a painful injection administered in the buttock each week. Further trials are already underway for longer-term injections combined with a pill and skin patches, which are expected to take eight years to complete.
The contraceptive works by secreting the male hormone testosterone into the body to reduce his sperm count to a negligible amount. It fools the man's body into believing it has already produced adequate levels, because there is so much of the hormone in his system.
In previous tests the researchers had already discovered that sperm counts in 60 per cent of men could be reduced to zero by weekly injections, and this could be achieved without affecting their sex life.
The new tests have revealed that it could be effective in a further 38.6% of men by reducing the sperm count to a newly-discovered critical level. This had a failure rate of only 1.4 pregnancies in 100 couples.
Among the men who did not find success with the male contraceptive during trials was Kevin McQuaide, 41. He was one of 29 volunteers at St Mary's Hospital, Manchester, involved in the 18 month trial.
He received the weekly injection from September 1993 and by March 1994 his sperm count had dropped from 40m to 200,000. Doctors declared him infertile, only for his wife to discover she was pregnant seven months later.Reuse content