GCHQ has not been using a controversial US internet monitoring programme to dodge tough legal checks on their activities, William Hague has insisted.
The Foreign Secretary refused to confirm or deny details of the eavesdropping agency's links to the Prism spy scheme, but said the law-abiding British public had "nothing to fear" from their work.
Speaking on the BBC's Andrew Marr Show, he also confirmed he would be making a statement to the Commons on the issue on Monday.
Mr Hague said: "As someone who knows GCHQ very well... the idea that in GCHQ people are sitting working out how to circumvent a UK law with another agency in another country is fanciful. It is nonsense."
The Cabinet minister declined to confirm that he had personally authorised engagement with the US Prism programme.
But he said checks in place in this country, including reviews of decisions by the Interception Commissioner, were strong.
"That legal framework is strong, that ministerial oversight is strong," he said.
"The net effect is that if you are a law abiding citizen of this country going about your business and personal life you have nothing to fear about the British state or intelligence agencies listening to the content of your phone calls or anything like that.
"Indeed you will never be aware of all the things that these agencies are doing to stop your identity being stolen or to stop a terrorist blowing you up tomorrow."
Mr Hague said it would "defeat the object" to reveal how GCHQ or the security services work, because it would help terrorist networks, criminal networks, and foreign intelligence agencies.