The Press Complaints Commission has opened an investigation into The Daily Telegraph’s use of “subterfuge” in a series of undercover stings – one of which led to Business Secretary Vince Cable telling reporters he had “declared war on Rupert Murdoch”.

The press standards watchdog confirmed that Tim Farron, president of the Liberal Democrats, had asked the body to conduct an investigation into the actions of the Telegraph Media Group after its reporters posed as constituents to secretly detail conversations with several leading Lib Dems during constituency surgeries.

One of these sessions took place in Cable’s Twickenham constituency where he made his comments about Rupert Murdoch and indicated he could seek to block the proposed takeover of BSkyB by the media mogul’s News Corporation.