The Press Complaints Commission (PCC) is to investigate the Daily Telegraph's use of undercover reporters to record Liberal Democrat MPs after an official complaint from the party.
Liberal Democrat president Tim Farron had written to the press watchdog to investigate the undercover stings carried out by journalists at the surgeries of MPs.
Business secretary Vince Cable was one of a string of Liberal Democrat ministers to be taped by the Daily Telegraph posing as constituents.
He told reporters he had "declared war" on Rupert Murdoch's media empire.
Cable was rebuked by the prime minister and stripped of his responsibility for media competition after his unguarded comments on the coalition and media baron Murdoch were revealed.
Over 200 complaints had been received by the PCC after the stories were published in December.
A PCC spokesman said: "We have now received a letter from the Liberal Democrats asking us formally to investigate. We will do so under clause 10 (Clandestine devices and subterfuge) of the Editors' Code of Practice."
During questions on Commons business, the Daily Telegraph was criticised by a member of the Cabinet.
Commons Leader Sir George Young told MPs that tactics used by the paper damaged the relationship between constituents and MPs.
He said: "I think members from both sides of the house should be concerned about the tactics that were used.
"I think journalists posing as constituents when they are not, raising fictitious cases with MPs, taping them without their knowledge - I think this all risks prejudicing the relationship between a member of Parliament and his constituent at his advice bureau. And it doesn't seem to me to be responsible journalism."


Have your say...
Please enter your comments below.