The press watchdog is to investigate after the Daily Telegraph used undercover reporters to record Liberal Democrat ministers' comments on the coalition Government.

Twickenham MP Vince Cable was one of a number of Lib Dems secretly recorded making unguarded remarks last month.

The Business Secretary was taped “declaring war” on Rupert Murdoch by the reporters, who pretended to be constituents.

The remarks led to him being stripped of his powers to rule on Murdoch's bid to take control of BSkyB.

Speaking to the Richmond and Twickenham Times after the story broke, Dr Cable claimed the Daily Telegraph had “completely undermined” the work of MPs.

The Telegraph said its story was in the public interest and it would co-operate with the probe.

A spokeswoman for the Telegraph Media Group said today: "The Telegraph always abides by the terms of the Editors' Code and co-operates fully with the work of the PCC.

"We will of course assist their investigation on this complaint in any way we can.

"We are satisfied we acted within the terms of the Code as we believe there is a strong public interest in our publishing this story.”

Other Lib Dem ministers targeted were Norman Baker, David Heath and Paul Burstow.

The Press Complaints Commission today confirmed it would carry out an investigation after Lib Dem president Tim Farron made an official complaint to the press watchdog.

Two hundred people have contacted the PCC over the story.

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."