The BBC's Fergus Walsh on frozen eggs

Mohammed Taranissi, director of the Assisted Reproduction and Gynaecology Centre in London, said the process would help women undergoing cancer treatment and career women to have children in later life.

The service, which costs £2,800 a year, became available this week when the centre was awarded the first licence in the UK to freeze human eggs.

However, the licence does not allow the clinic to thaw or fertilise the eggs as authorities have yet to be convinced that the technology to do so is safe.

Commercial trading

Critics say the process could be the start of commercial trading in human eggs.

Anti-abortion group the Society for the Protection of the Unborn Child (SPUC) says there shoud be much more research into the long-term effects of freezing any part of the reproductive process, including embryos which began to be frozen 15 years ago.

Radiotherapy can damage women's ovaries

This should include research into the effects on both mother and child.

A spokesman said: "The current practice of creating embryos from eggs and storing them long-term is very risky for the embryos concerned.

"Most die. There needs to be a thorough follow-up of those who don't to see if there are any additional risks."

He added that great pressure was being put on women to donate eggs for infertile couples. SPUC believes many of the eggs are being used for research, including genetic testing.

He said donors' consent needed to be obtained by clinics, but he thought legislation should be tightened so that consent did not give scientists "carte blanche" to dispose of donated sperm and eggs.

He was also concerned about the possibility of a woman who stored her eggs dying or becoming incapacitated.

"I can see situations arising where her partner would have to use a surrogate mother to carry the frozen egg without the dead woman's consent," he said.

Cancer

Mohamed Taranissi on the BBC's Today programme

Other critics question the morality of having 'convenience' babies, saying it takes away the woman's personal responsibility.

But Mr Taranissi said the treatment would help women who have been diagnosed with cancer and are likely to be made sterile by the chemotherapy or radiotherapy they will receive.

Mohammed Taranissi: women can wait until they find the right partner

He said: "This will be of help to women who have cancer and need to undergo chemotherapy or radiotherapy, because of the damaging effect such treatment has on the ovaries.

"There is nothing you can offer them at present. Once the damage is done they are doomed for the rest of their life.

"Now it is possible to take their eggs before they start treatment and freeze them so they can be fertilised later."

He added that babies on demand was not a new situation.

"It is already happening. People are delaying parenthood and this is accepted by society already. There is nothing immoral about using technology to do this.

He said women who had delayed having babies because of their career were now using sperm donors to get pregnant.

"At least using this technique they will not be forced to use donated sperm. They can wait for the right time and the right person with the hope of raising their child in a family environment," he said.

But SPUC said it could only envisage it being used by women who had passed the menopause or elderly women who wanted a younger, surrogate mother to carry their baby for them.

"The whole process further opens the Pandora's Box of creating babies in laboratories," said a spokesman.

Licence to thaw

The new service will be open to women aged under 35 The eggs, which are stored in liquid nitrogen, are not intended to be kept for more than five years, although this may be extended in the future.

However, the centre has not yet got a licence to thaw the eggs.

The freezing of sperms and embryos is commonplace, but only a few clinics worldwide are allowed to freeze, store and thaw human eggs.

Eight babies have so far been born from frozen eggs and more women are pregnant. The process, which has only become possible in the last few years, is allowed in Australia, the USA and Italy.

Eggs are fertilised by microinjection

If a licence were granted, the frozen eggs would be thawed, injected with sperm by microinjection and implanted in the womb.

The Human Fertilisation and Embryology Authority (HFEA), which regulates assisted fertilisation in Britain, awarded the licence to freeze eggs but will not yet let them be thawed.

However, HFEA chief executive Suzanne McCarthy said: "That might change if we get enough scientific evidence and information proving that the technique is safe."

She added that she believed it was unlikely women who were naturally fertile would go through the stress, expense and uncertainty of freezing their eggs.

"This is not babies on a conveyor belt," she said.

So far no more than eight babies worldwide have been born from embryos created from frozen eggs.

The Assisted Reproduction and Gynaecology Centre has the highest success rate for live births following in-vitro fertilisation treatment.