Vince Cable said today his confidential relationship with constituents has been reinforced after a Daily Telegraph sting at his weekly surgery was found to have breached rules against using subterfuge.

The Business Secretary said he was “delighted” with the Press Complaints Commission (PCC) ruling, which said the newspaper had no justification for sending two undercover reporters to his office in Lion Road, Twickenham.

The journalists were trying to expose alleged discontent among Liberal Democrat ministers.

They secretly recorded the Twickenham MP saying that being in the coalition Government was "like fighting a war" and he could use the "nuclear option" of resigning. He also “declared war" on media tycoon Rupert Murdoch.

The PCC accepted the Telegraph's tactics in December last year had produced material that was "in the public interest".

Dr Cable today ruled out taking legal action against the newspaper and told the Richmond and Twickenham Times he hoped the PCC findings would restore trust between him and his constituents.

He said: “I’m delighted with the findings which fully vindicates the complaints I and my colleagues made to the PCC.

“It’s very rare the commission comes down so clearly and we are very pleased with the outcome.

“From my point of view as a local MP I’m particularly pleased that the relationship I was seeking to reinforce, which was my confidential and private relationship with individual constituents, has been recognised and supported by the commission.

“I hope that, particularly in light of this ruling, my constituents and others will be reassured that trust has not been undermined.

“It was important this was established by an independent, respected and reputable body.”

Tim Farron MP, president of the Liberal Democrat Party, took the case to the PCC which today upheld his complaint and ruled the Telegraph had launched "disproportionately intrusive attention" without sufficient reasons.

Dr Cable, who was stripped of media regulation powers after the sting - which he said had also caused “great damage” to his work with constituents - confirmed he was not considering taking the newspaper to court.

He said: “It’s a matter for the party to decide what action to take but I’m certainly not considering that.”

The Daily Telegraph told the PCC its sting had proved Lib Dem ministers "were not consistent in their private and public statements" about the coalition Government.

But the watchdog said the newspaper’s initial evidence was insufficiently strong to warrant the level of intrusion and that the ministers were asked "to comment on a series of policy issues with the evident intent of establishing on which subject they might say something newsworthy".