Women urged by fertility expert to bank ovaries in their twenties

While freezing eggs can offer women some peace of mind, storing larger pieces of the ovary guarantees thousands more eggs and a higher chances of having babies, he said.

Dr Sherman Silber, who carried out the world's first full ovary transplant, stressed that women in their 20s should be thinking of having the procedure before getting any older.

Banking a third of an ovary means about 60,000 eggs could be captured in the tissue, This would then be retransplanted when women are older, he said. The procedure would not affect their ability to conceive naturally.

Dr Silber said there were disadvantages to conventional egg freezing, which takes place at clinics in the UK.

He said: "The question is how many cycles of egg retrieval do you need to feel comfortable and secure that you have enough eggs?

"There's no absolute answer.

Dr Silber said women facing cancer treatment which could make them infertile should also bank ovarian tissue.

Worldwide, 23 babies have been born from ovary or ovarian tissue transplants, but only seven centres worldwide – and none in the UK – offer ovarian tissue freezing.

Tony Rutherford, chairman of the British Fertility Society, said he thought it was too soon to recommend widespread banking of ovarian tissue.

"We don't know how many people have had grafts and therefore we don't know how many have been successful and how many have failed," he said.

"If it's performed in lesser hands (than Dr Silber's) it might not be quite as effective."

He called for a worldwide register of procedures to be set up because "only then can we give patients realistic figures about whether it's going to work or not.

"We need to see clearer evidence of its effectiveness and that's what we don't have at the moment."

The calls came as a UK survey revealed many men whose fertility may be at risk from cancer treatment are not being offered the chance to bank their sperm.

Of almost 500 clinicians, more than a fifth were unaware of local policies on storing sperm and only a quarter of oncologists said discussions with male cancer patients about sperm banking were systematically documented.