It is illegal, completely illegal, in this country for people to buy and sell babies

Home Secretary Jack Straw

Alan and Judith Kilshaw, of Buckley, North Wales, bought the girls from a US baby broker who is accused of having already sold them once to another couple from California.

The Kilshaws are now applying for British citizenship for six-month-old Belinda and Kimberley, who currently have six-month tourist visas.

'Huge concern'

Mr Straw said it was illegal for British citizens to buy babies.

"It's a matter of huge concern. I share that concern as a parent as much as a senior minister in this government," he said.

"It is illegal, completely illegal, in this country for people to buy and sell babies or children, and that is entirely as it should be, because it is frankly a revolting idea."

Mr Straw added: "We shall of course be looking at precisely what happened in these circumstances and I will be consulting colleagues about it.

"Obviously, what happened, happened in other jurisdictions in the United States, but nonetheless we need to look at the circumstances.

"There is also an issue of immigration control," said Mr Straw.

Mr and Mrs Kilshaw maintain they legally adopted the twins.

The couple are planning to fight for custody of the two babies after a US family laid claim to them.

They are also believed to be the focus of an investigation by the US Federal Bureau of Investigation (FBI).

The US family claims they had already paid �4,000 to an internet adoption broker for the twin girls.

'Internet adoption'

The Kilshaws say they planned the adoption on the internet while the twins were still in an American hospital after being born prematurely.

"We said we would consider the twins and would like to adopt them," Mrs Kilshaw told the BBC.

The Kilshaws say they have nothing to hide

"They had to stay in hospital the full term. Then we were told they were placed."

Mr and Mrs Kilshaw, who have three children and had tried IVF treatment to have more, said the Californian family had not adopted the girls.

Mr Kilshaw said he believed the mixed race twins would face less racial prejudice in this country than in the United States.

He said he and his wife had been forced to seek adoption in the US because of the "over-regulated" process in the UK.

Mr Kilshaw said he had always wanted a daughter and realised that he and his wife were unlikely to conceive naturally.

"Adoption in Britain is over-regulated and people are regarded as being unsuitable for silly reasons," he said.

Asked about the threat of a FBI investigation, Mr Kilshaw said: "We have nothing to hide."