Around 60 couples in Manchester and 20 in Edinburgh have volunteered to be a part of year-long trials in which the scientists will try to prove a new contraceptive method to be as effective as the Pill which is often linked to breast cancer and fatal blood clots.

The contraceptive, given in two injections every two months, contains testosterone, the male sex hormone and a man-made version of the female sex hormone Progesterone, and tricks the brain into shutting off sperm production. The sperm counts rapidly return to normal once the injections are stopped. But it does not protect against sexually transmitted diseases such as Chlamydia.

Professor Richard Anderson, from the University of Edinburgh, who is heading one of the trials said, "When we carried out surveys of women, they were enormously enthusiastic to share the responsibility of contraceptive".

He added that the jab would appeal more to those in a committed relationship as those in a strong relationship share everything, and the contraceptive was a part of it.

It has been reported that the injection has proved effective in 99 % of cases. Although some men might experience hot flushes, mood swings or acne, yet no serious side effects are expected.