The Press Complaints Commission might be on its way out, but it has done a service to British society by recognising that there are times when journalists must go undercover to reveal the secret machinations of the political system.

The latest adjudication is a fine one – and not just because it finds in favour of The Independent's decision to publish covertly obtained details of the working methods of the lobbying company Bell Pottinger. More importantly, the ruling will give pause to those in power who might otherwise think their activities are beyond the gaze of public scrutiny.

Much has happened since The Daily Telegraph's 2009 exposé of MPs' expenses claims gave a wake-up call to those in Westminster who thought they could escape being held to account. The phone-hacking scandal and evidence from the Leveson Inquiry have damaged the reputation of the press and weakened journalists' claims that sometimes devious methods must be allowed in the public interest.

It will always be a matter of judgement. Last year, the Telegraph had its knuckles rapped by the PCC for using subterfuge to expose Vince Cable's views on Rupert Murdoch. This time, it has recognised that the public interest is served by exposing a lobbying and public relations industry that has become immensely powerful – a fact that must also bear on Lord Justice Leveson's considerations. The misdemeanours of lobbyists and PR companies might not be on the scale of phone hacking; but, as Bell Pottinger staff admitted, their sector too has its "dark arts".

The reports by the Bureau of Investigative Journalism and The Independent shone a light on links between lobbyists and government, and also revealed how spin-doctors manipulate internet information sources such as Google and Wikipedia. The PCC saw the clear public interest in such revelations. And as Lord Justice Leveson prepares to define the future of press regulation, they are also a poignant example of how the regulator's work amounts to so much more than settling disputes between TV stars and the paparazzi.