UK listening centre GCHQ is handing a report to MPs today over its role in the US Prism spying effort.
Foreign secretary William Hague told parliament yesterday that allegations GCHQ circumvented the law to gain information on UK citizens are "baseless".
He was referring to almost 200 intelligence reports requested by UK spying agencies in a 12 month period via the secret Prism programme.
A large chunk of the information in the reports is believed to have been generated from data taken from leading web and technology companies like Google, Yahoo, Facebook, Apple and Microsoft.
Ex-CIA worker and whistleblower Edward Snowden, now in hiding after checking out of his Hong Kong hotel bolt-hole, claims US agencies gathered and shared phone records and internet data with allies using Prism.
Hague refused to confirm nor deny claims that GCHQ has had access to Prism records since June 2010. Hague said any data obtained by the UK from the US involving UK nationals was "subject to proper UK statutory controls and safeguards".
If the intelligence agencies in the UK need information on UK individuals through spying they officially need ministerial approval, so the suggestion from some quarters was that they got the Americans to do it for them instead, via Prism.
That said, in some circumstances UK intelligence agencies simply contact a phone or web company and ask for, and often get, the information they want without much problem. When BT had a monopoly over communications in the UK, and before the internet, it was a lot easier though.
Prism is said to give the US National Security Agency (NSA) and the FBI easy access to the systems of nine of the world's top web and technology companies.
All the companies deny giving Prism "access to their servers".