Wealthy British couples who cannot have children are increasingly seeking "wombs for hire" from women overseas, according to figures obtained by The Independent.

The number of couples formally registering children born to foreign surrogates has nearly trebled in five years, raising concerns that poor women in developing countries are being exploited by rich Westerners.

"Parental orders" granted following surrogacy – to transfer the child from the surrogate mother to the commissioning parents – have risen from 47 in 2007 to 133 in 2011.

While the figures are still relatively small, experts say they understate the true scale of the trade which is driven by agencies operating in countries such as India, drawn by a lack of red tape and the absence of regulation.

There are parallels with the trade in inter-country adoption 20 years ago, when hundreds of children from impoverished families in eastern Europe and the developing world were "sold" to wealthy foreigners, with few checks on their suitability, they claim.

Commercial surrogacy is permitted in the US and in many other countries including India, where it was legalised in 2002.

But it is banned in Britain and only expenses may be paid – making it difficult for UK couples where neither partner is able to bear children to find women prepared to volunteer for the role.

In 2010 the law was changed to allow gay and lesbian couples and unmarried heterosexual couples to use surrogates for the first time, boosting demand further.

Events such as the Alternative Families Show, which acts as a showcase for surrogacy agencies overseas, regularly draw large crowds. The impact can be seen in the increasing numbers of wealthy British couples who are going abroad where there are fewer restrictions and a surrogate womb can be rented from £10,000 to £20,000. Some do so after trying and failing to have a baby by in-vitro fertilisation, directed by doctors who have been treating them.

"We have clinicians in this country who have links with overseas clinics. That was stopped with international adoption years ago. I don't think the Human Fertilisation and Embryology Authority has been strong enough on this," said Marilyn Crawshaw, senior lecturer in the University of York's department of social policy, who published the figures on parental orders in the Journal of Social Welfare and Family Law.

"There is concern about child trafficking. The World Health Organisation held a meeting on this. One report described a surrogacy ring in Thailand in 2011 in which 13 Vietnamese women, seven of them pregnant, had been trafficked for the purpose of acting as surrogates. Other reports have highlighted concerns about the exploitation of Indian surrogates."

Ms Crawshaw said evidence suggested that the number of children born in India to commissioning parents from the UK was "well in excess" of the cases known to official sources, making monitoring very difficult.

"US social workers have warned that the decline in inter-country adoption may be leading to its replacement by global surrogacy as the preferred route for those wanting to build their family with a 'healthy' infant but with no less concerns among professionals as to associated ethical dilemmas and human rights concerns," she said.

Natalie Gamble, a lawyer specialising in surrogacy cases, added: "We have got this phenomenon where people can go overseas and do deals with commercial agencies and then come back and ask for a parental order.

"The law of our land says you cannot buy and sell babies. But the judges end up granting the parental order, with just a rap on the knuckles for the parents, on the grounds that the welfare of the child is paramount.

"When people went overseas to adopt, safeguards were put in place to stop the buying and selling of children. Are we going to have the same problems again with overseas surrogacy?"

Case study: 'It was awkward when the mother had to hand over our twins'

We both found it very hard to keep it together. It was a very emotional time. We could never have imagined it a couple of years ago."

Stephen Hill and his partner Johnathon Busher first held their twin girls in their arms less than 12 hours after their birth in a Delhi hospital last April.

The gay couple, from the West Midlands, had been together for 18 years when they decided they wanted a family.

In 2011, they travelled to India and agreed a contract with a clinic in Delhi where Mr Hill's sperm was used to fertilise an egg from a donor they had selected, and the resulting embryo was implanted in a surrogate mother.

When the twins were born there was an "awkward moment" before the surrogate mother agreed to hand them over, as her husband had been telling medical staff the infants were his own.

"She was reminded that it was a deal and she was fine. She was a little bit too attached and she needed to be reminded," Mr Busher said. "We produced the contract and we were able to take them out of the hospital. We were so happy our feet didn't touch the ground."

Surrogacy laws: Britain and India

Commercial surrogacy

UK – illegal

India – legal

Advertising

UK – not permitted

India – permitted

Enforceable agreement

UK – no

India – yes

Payment to surrogates

UK – expenses only