The Government tonight came under pressure to debate why the US monitoring base Menwith Hill is to be used in a controversial missile defence programme.

Speaking in his debate on the US missile defence system, Lord Wallace of Saltaire said he hoped the Government would be shamed into providing a "fuller and more detailed justification of its decision" of why the RAF site near Harrogate is to play a part in the US National Missile Defence scheme, know as Star Wars'.

Lord Saltaire said that, amid persistent rumours the Government was negotiating with Washington for a major role in the US system, Defence Secretary Des Browne assured the Commons as late as April last year that "the UK has received no request from the US to use Menwith Hill for missile defence-related activities."

The Lib Dem Lord criticised the statement as "misleading", with formal letters on the use of Menwith Hill only exchanged two months later.

And he called for clarification over the status of the base after contacts at Harrogate Council told him the number of people at the site increased by hundreds after September 11.

Baroness Crawley, responding for the Government, said members of both Houses had been given the opportunity to question defence ministers about the plans.

She told peers: "The original decision to allow the US to use RAF Menwith Hill as a relay station for satellite data was taken in March, 1997.

"What the UK agreed to recently was that the US could use this same satellite data in their missile defence system."