Edinburgh West MP Mike Crockart has spoken out against controversial plans that could allow the government to monitor e-mails, texts and calls of everyone in the UK.
The Libe Dem is one of 16 MPs to pen a joint letter setting out their concerns at the plans.
Mr Crockart said: “Liberal Democrats have a proud history of defending civil liberties, both in opposition and in government. We opposed the Labour government’s undermining of data privacy in 2009 and since taking office in 2010 we have turned back the tide of Labour’s erosion of these liberties.
“At our recent party conference we called for stronger safeguards on existing surveillance measures.
“Any proposed changes must be openly and publicly discussed and debated and safeguards must go further than the current weak controls.”