The UK and US have been engaged in talks over the so-called Son of Star Wars missile defence system.
Downing Street confirmed today that discussions have taken place, although refused to comment as to whether the prime minister had been personally involved in lobbying Washington to site part of the ballistic missile defence system in the UK.
"We have certainly been engaged in conversations with the US about this," a spokesman said.
"The objective of these conversations was to make sure that the UK is kept in consideration to be one of the locations for the system should the US press ahead with the system."
The move is likely to anger environmental and anti-nuclear campaigners and the Liberal Democrats argue that it is an attempt by Blair to create his legacy.
Lib Dem defence spokesman Nick Harvey said: "As with Trident, Tony Blair appears to be in a desperate rush to hurry through vital security decisions behind closed doors.
"Obsessed with his legacy, the Prime Minister has succumbed to a bunker mentality."
Questioning Downing Street's claims that the missile defence system is a security issue, Mr Harvey continued that any system that damages the nuclear non proliferation treaty would make Britain less safe.
He called on the government to put British national interests ahead of the "interests of the arms industry and US".
The Conservatives queried why so little had been heard about the plans until they were reported in today's Economist. Speaking to Radio 4's Today programme, shadow defence secretary Liam Fox said they has asked "a lot" of questions in parliament but received no details from the government.
"If the government really do want to maintain what they regard as a bipartisan approach to defence in this country, they better start getting honest with the opposition," he said.
According to statements from both the UK and the US, the proposals are still in the planning stages and it is reported that the US is primarily interested in sites in the Czech Republic and Poland.