Scientists have made a breakthrough which could be key to developing a male contraceptive pill.

The discovery uses a peptide which changes the way human cells work, “switching off” sperm’s ability to swim, to render men temporarily infertile.

Scientists hailed the results as “startling – and almost instant.”

It raises the prospect of a fast-acting pill or a nasal spray that a man could take hours or even minutes before sex.

Women are typically advised to stop taking the Pill weeks or even months before trying to conceive.

But researchers believe the effects of a male pill would happen almost instantly, with effects wearing off within a matter of days.

Family planning experts said a reversible male contraceptive could help men control their fertility, and benefit couples where the woman does not want to take the Pill.