Researchers at St Mary's Hospital, Manchester, are confident that their new male contraceptive implants will succeed where other techniques have failed.

They have taken a fresh approach to the problem of unreliability in male pills.

Back-up system

Up until now, while female contraceptive pills are about 99% effective, their male equivalents lagged behind, proving to be only 70-80% reliable.

Scientists decided that the reason for this must be that men had a back-up system, so that when one hormone knocked out sperm production, another part of the brain kicked in and took over.

Previous attempts have failed to stem the secondary sperm system

The Manchester team has now come up with a combined hormone approach that tells both centres in the brain to stop producing sperm.

Dr Morton Hair, one of the research team, said: "We have high hopes that this will work.

"Our aim is to produce something on a par with the female pill.

"It's not easy to design a male contraceptive. All you have to do with women is to knock out the production of one egg per month, but men produce something like 250 million sperm cells per ejaculation.

Volunteers required

"Suppressing this gigantic factory of sperm production in men is a lot more difficult.

"To get something that gives you the security of a female contraceptive you have to virtually stop all sperm production."

The team is now trying to recruit at least 60 volunteers for the six month trial.

They should be aged 19 to 50 with a minimum sperm count of 20 million per millilitre.