The Ministry Of Defence has denied reports that American interceptor missiles are to be stationed on British soil.
RAF Fylingdales is being upgraded with new technology
The Independent on Sunday says Tony Blair has agreed a secret deal with the US to base missiles at RAF Fylingdales in North Yorkshire.
The weapons would allow the US to destroy incoming missiles and form part of the new US missile defence system.
But a Ministry of Defence spokesman said no formal approach had been made.
A spokesman for the MoD said: "We are not to going to comment on this alleged secret deal.
"What we will say is that no formal approach has been made to the UK to base missiles here.
"Nor have we decided whether we need our own missile defence system here in the UK."
Work has already started on a £449m project to upgrade RAF Fylingdales to make it part of the US anti-missile defence programme.
But until now, the government has only confirmed it will allow the US to use early warning radar at the base.
Missiles are currently being located by the US in Alaska and California, but it is thought the Pentagon wants to station more in Europe.
Workmen install an interceptor missile in Alaska
In August the Danish Government signed a deal to allow a radar base in Greenland to be used, but the US did not ask to site missiles.
According to the Independent on Sunday, the deal to permit missiles was brokered in Washington last May by senior official from the British Embassy and the US State Department.
It is reported the British agreed the deal in principle, but asked that it be kept under wraps until after the next election.
Liberal Democrat foreign affairs spokesman Sir Menzies Campbell said: "These reports, if true, are a source of grave concern given that a decision appears to have been taken behind closed doors before a full public debate on the costs and strategic implications.
"This could have major implications for the defence posture of the UK, our relationship with NATO countries and other allies."
The plans were also condemned by Labour left-winger Diane Abbott.
"It is another example of how we appear to be in the pocket of America," she told BBC1's Breakfast with Frost programme.
"We have no national interest in having American missiles on British soil."