The UK will not block use of the death penalty by the US in the case of two men who are accused of being Islamic State members, the home secretary says. Photo: Internet Source

In a letter to the US attorney general, leaked to the Telegraph, Sajid Javid said the UK will seek no assurances that the pair will not be executed.

Alexanda Kotey and El Shafee Elsheikh were captured in Syria in January.

Number 10 said the PM was aware of the letter and discussions with the US on this issue were continuing.

Shami Chakrabarti, Labour's shadow attorney general, said Mr Javid had "secretly and unilaterally abandoned Britain's opposition to the death penalty" and appeared to be encouraging "this grave human rights abuse".

The men, from west London, are accused of being the last two members of an IS foursome dubbed "The Beatles".

Earlier this year, in an interview with Associated Press, they complained that they would not get a fair trial because the UK government had stripped them of their British citizenship.

The BBC's security correspondent Frank Gardner said if the pair were sent to the controversial US military prison Guantanamo Bay - where suspects have been detained without trial - the UK would withhold intelligence.

In the letter to Jeff Sessions, dated 22 June 2018, Mr Javid wrote that the UK would not seek "assurances" over the death penalty in this particular case, but said it did not mark a change in UK policy.

"I am of the view that there are strong reasons for not requiring a death penalty assurance in this specific case, so no such assurances will be sought," he said.

But the former independent reviewer of terrorism legislation, Lord Carlile, described the letter as "extraordinary".

"We do not extradite people to countries where there is a death penalty unless there is an assurance the death penalty will not be carried out," he told the BBC.

"This a unilateral change of policy without any consultation and I would be amazed if this had been approved explicitly by the prime minister."