by LUCY ELKINS, Daily Mail

Scientists claim to have developed a male contraceptive that not only offers 100 per cent protection, but also has no side effects.

But what will it do to the body and can it really be compared with the female Pill? We investigate.

What's in it?

It consists of a synthetic form of the female hormone progestogen, as well as a separate dose of the male hormone testosterone.

How does it work?

The progestogen shuts down the production of sperm in the testes.

Each sperm has a lifespan of 70 days from production, so the treatment must be taken for three months before it will be effective.

How is it taken?

In the most recent Australian trials the progestogen is given as an injection every three months.

The testosterone is given as an implant which is renewed every three months.

In the UK, tests have been carried out using testosterone and progesterone - the hormone from which progestogen is made - implants.

So far they have not been combined as researchers are still trying to perfect the dose individually before they unite them in a single treatment, delivered as a pill.

The female Pill is normally given in tablet form that has to be taken at roughly the same time each day.

Does it affect libido?

Traditionally male 'Pills' have substantially reduced sex drive which has discouraged many men from wanting to take it.

But in this case it does not appear to be true and the additional testosterone injection or implant helps maintain normal sex drive. Indeed, volunteers who tried the latest combination treatment reported that they found it actually increased their libido.

How effective is it?

The latest study in Australia found the contraceptive to be almost 100 per cent effective. However, studies using similar treatment in the UK last year found that it had a 93 per cent success rate at halting sperm production.

The female version is 99 per cent effective.

What are the side effects?

The latest trials claim that the treatment is 100 per cent clear of side effects, however further research is needed to confirm this.

Without the added testosterone, men could suffer weight gain, moodiness in addition to a reduced sex drive.

What are the main advantages of taking it?

The research so far suggests that as well as offering almost complete protection against pregnancy, it is also risk free.

An implant will also help reduce the risk of men forgetting to take a daily pill.

Research also suggests that taking it may keep men more youthful - and therefore more attractive to women - as it cuts the production of testosterone, which is thought to contribute to the male ageing process.

How soon is fertility restored after coming off it?

During the latest trial, full fertility was restored within seven months of coming off the treatment.

This is the time needed for natural testosterone levels to be restored, and the sperm to be produced and mature.

Some women find their normal cycle returns immediately after they stop taking the Pill - but most will be back to full fertility within six to eight weeks.

Who is it best for?

The treatment is an ideal alternative for any man who already has a family, especially those considering a vasectomy, which is not reversible. The female Pill is ideal for any age group.

Who is it not suitable for?

As with the female Pill, it would not be suitable for any man with hormonal problems.

Unlike a condom it will also not offer protection from sexually transmitted disease so may not be appropriate for sexually active men who are not in a long-term relationship.

When will the male pill be available?

It is hoped that a pill or implants may be available within three to five years.