Researchers at Oxford University claim they have discovered a drug which could become the male contraceptive pill within the next decade.

Unlike the female pill, which mimics a woman's hormonal balance to prevent her becoming pregnant, the male equivalent would not need to use hormones to disrupt fertility.

It also has few side effects and is completely reversible.

Scientists at the university's Glycobiology Institute, in South Parks Road, have been studying a treatment containing a substance called NB-DNJ, which interferes with the development of sperm cells.

It makes them poor swimmers, unable to propel themselves towards the egg.

Unlike other male contraceptives which are being tested, it does not need to cut off production of testosterone -- the hormone which gives men their masculinity.

Dr Frances Platt, reader in glycobiology, who led the researchers, said hormonal drugs could give men's bodies female characterisitics.

She said: "If you switch off testosterone, you have to replace it elsewhere."

NB-DNJ has so far only been tested on mice, which became infertile after being treated for three weeks, even though their testosterone levels remained unaffected.

The contraceptive effect could be reversed within four weeks of stopping the drug.

Dr Platt said: "We think that this treatment may work for men because the formation of sperm is very much the same process for all mammals. However, we need to evaluate it for men before we know for certain. If we see the same effects, then this could become a potential male contraceptive pill for the future."

The treatment has already been licensed for other conditions, so it could be tested on men in the next two years.

If trials succeed, the drug could be available within 10 years.