Andrew Grice: It's time to take a step back, Mr Cameron

"Hand on heart, we all did a bit too much cosying up to Rupert Murdoch," David Cameron told MPs on Wednesday. "No we didn't," mouthed Nick Clegg, sitting next to him at Prime Minister's Questions. He has never contradicted Mr Cameron like that before.

Mr Clegg is right. The only time right-wing newspapers took much interest in the Liberal Democrats was during the brief outbreak of "Cleggmania" during the 2010 election campaign. They dug fruitlessly for scandals about Britain's third party because they didn't want the hung parliament the public duly voted for. There was never much point in the Lib Dems cosying up to the Murdoch empire; the feeling was mutual.

All that changed when the Coalition was formed. The mountain of evidence presented to the Leveson Inquiry this week shows that Mr Murdoch's News Corp expected the Lib Dems to behave just like the Conservatives and Labour – even on the highly sensitive issue of the company's attempt to buy the 61 per cent of BSkyB it did not own. Team Murdoch seemed surprised and disappointed when the Lib Dems spurned their advances. Vince Cable, the Lib Dem Business Secretary, declined to meet James Murdoch.

Emails presented to the Inquiry show that as Mr Cable weighed up the takeover bid in November 2010, his special adviser Giles Wilkes refused to meet Frédéric Michel, News Corp's head of public affairs.

The following day, Mr Michel had better luck: he was granted a meeting with Rupert Harrison, special adviser to George Osborne. Later that month the Chancellor met James Murdoch, who lobbied him to support the bid and complained about the "slow progress" on Mr Cable's decision.

One civil servant told me: "News Corp found the front door closed by Vince Cable, as it should have been. So it immediately went round the back door to George Osborne." Treasury sources insist that the Chancellor played no part in deciding on the takeover, although the word in Whitehall is that he was instinctively supportive. So was Jeremy Hunt, the Culture Secretary, who took over responsibility for the bid decision in December 2010 when Mr Cable shot himself in both feet by telling uncover reporters he had "declared war" on Rupert Murdoch.

It is an open secret that Mr Cable would almost certainly have taken Ofcom's advice and referred the BSkyB bid to the Competition Commission, the last thing News Corp wanted. Mr Hunt was much more sympathetic to the bid. While Mr Cable was still in the driving seat, the Culture Secretary was very keen to talk to him about it in the margins of Cabinet meetings. I'm told he didn't put him under pressure on his decision but wanted to know about the process and the timing.

Even allowing for a PR man's hype to his bosses in Mr Michel's emails, the constant contact between him and Mr Hunt's office over the bid is astonishing. The Culture Secretary did not give News Corp all it wanted immediately but he appears to have bent over backwards to help it reach its goal. We await Mr Hunt's appearance before Lord Justice Leveson, but his direction of travel suggests he would have approved the takeover – until it was stopped in its tracks by the chilling revelation that Milly Dowler's phone was hacked by the News of the World.

After a bold intervention by Ed Miliband, determined to show that his approach to Mr Murdoch was different to that of Tony Blair, Gordon Brown and David Cameron, News Corp withdrew the bid, and the Leveson Inquiry was set up.

Even if some evidence presented this week is challenged, the different approach to the Murdoch empire by the Conservatives and Lib Dems is unmistakable. Mr Cable's political team at the Department for Business, Innovation and Skills (BIS) was advised by civil servants to be very careful about their contacts with interested parties and the media. It was such a sensitive issue that they knew anyway. What is interesting is that the very same civil servants transferred to Mr Hunt's Department for Culture Media and Sport (DCMS), which took charge of all media regulation from BIS as well as the BSkyB decision. So it is highly likely that these officials urged Mr Hunt's political advisers to be cautious about the takeover too. The emails released to Leveson show that such advice was ignored.

Mr Cable's evidence to the Inquiry will be fascinating. You could argue that the Business Secretary's foolish remarks about his "war" with Rupert Murdoch were just as bad at one end of the spectrum as Mr Hunt's pro-Murdoch stance at the other. Both cabinet ministers appear to have an agenda stemming from their parties' very different instincts: the Lib Dems' tradition of backing media plurality and the Tories' decision to copy New Labour by cuddling up to the Murdochs.

One lesson from the sorry saga already exposed by the Leveson evidence is surely that politicians should no longer make impartial quasi-judicial decisions on issues like media ownership. They should be left to regulators like Ofcom. The Lib Dems and Labour support that. If Mr Cameron is serious about not "cosying up" to media owners, he will follow suit.