Lord Ashdown criticised scaremongering by "lazy politicians" who frighten people into thinking "al Qaida is about to jump out from behind every bush and therefore it is legitimate to forget about civil liberties" in a newspaper interview published online last night.
Although Lord Ashdown -who led the LibDems from 1988 until 1999 - said he was speaking for himself, his views are understood to be shared by other senior members of the party.
He is the latest senior politician to demand a review of the powers of Britain's intelligence agencies - GCHQ, MI5 and MI6 - and the laws and oversight which underpin their activities.
He said surveillance should only be conducted against specific targets when there was evidence against them. Dragnet surveillance was unacceptable, he added.
He also criticised the Labour party, which was in power when the agencies began testing and building many of their most powerful surveillance capabilities.
Labour's former home secretary Jack Straw was responsible for introducing the Regulation of Investigatory Power Act 2000 (Ripa), which made the programmes legal. He said: "Ripa was a disgraceful piece of legislation. Nobody put any thought into it. Labour just took the words they were given by the intelligence agencies."
He said he was "frightened by the erosion of our liberties".