Tom Watson, a former defence minister and deputy chairman of the Labour Party, said there was an urgent need for “public scrutiny” of the activities at RAF Croughton, a US Air Force base in Northamptonshire which is a major hub for American military and clandestine communications.
The Independent revealed this week that the base is used to route vast amounts of data captured by Washington’s “Stateroom” network of listening posts in diplomatic premises back to America for analysis by the CIA and the National Security Agency.
The network is at the centre of revelations that the NSA intercepted a mobile phone used by Mrs Merkel. A spying “nest” on the roof Washington’s Berlin embassy appears to have been abruptly turned off last week following an incendiary row between Germany and America about the eavesdropping.
Documents provided by NSA whistleblower Edward Snowden imply that any material gathered from the Berlin embassy listening post would have been relayed back to a joint CIA/NSA facility in Maryland via a secure link within RAF Croughton.
In a letter copied to members of Parliament’s Intelligence and Security Committee ahead of Thursday’s appearance by the heads of Britain’s three main spying agencies, Mr Watson said The Independent’s revelations added to existing concerns that RAF Croughton is used as a support site for US drone strikes in Yemen.
The MP said: “The use of RAF Croughton by the NSA, CIA and other US officials puts our country at real risk of complicity in both unlawful eavesdropping and the unlawful killing of civilians overseas by the US. These allegations also undermine our relations with other key allies.
“The time has come for the use to which RAF Croughton is put to be subject to public scrutiny - proper investigation is needed.”
Mr Watson asked Mr Hague to make a statement to the House of Commons outlining Government policy regarding the apparent use of RAF Croughton and other US-manned bases to assist Washington’s embassy-based listening operation, which is run in parallel with a similar British network run by GCHQ.
He also asked for the matter to be raised with US Secretary of State John Kerry.
An FCO spokesperson said: “In line with long-standing practice we do not comment on intelligence matters."