David Cameron's apparent admission that he did discuss Rupert Murdoch's bid for BSkyB with unnamed executives of News International casts the first serious doubt about the conduct of the prime minister and the government over the proposed £8bn takeover that would have led to the creation of most powerful media group in Britain.

Asked seven times about his involvement in the bid – which needed regulatory approval initially from business secretary, Vince Cable, and later the culture secretary, Jeremy Hunt – the prime minister cracked, indicating that he may well have had one or more conversations with individuals at Murdoch's News International who he did not get close to naming.

Labour's Dennis Skinner asked if the prime minister had ever discussed the BSkyB bid in any of his meetings with News International. Cameron said he never had any "inappropriate conversation" with News International and had taken himself completely out of any consideration of the BSkyB deal – and noted that Sir Gus O'Donnell, the cabinet secretary, had ruled "very clearly" that no ministerial code was broken in relation to the BSkyB merger and meetings with News International executives.

However, as with his answer to an earlier question on the same subject from Ben Bradshaw, the implication was clear. There had been some sort of conversations, most likely with Rebekah Brooks, the former News International chief executive – we shall see if that detail emerges later – perhaps at one of those meetings last Christmas that Brooks and Cameron were desperate to keep concealed until this week.

The question raised is, what was discussed, and whether Brooks or whoever sought to bring Cameron's influence on to a process that in law is supposed to be handled by just one minister – initially the Lib Dem Cable but, in the critical phase from December, the Conservative Jeremy Hunt. After all, getting the Sky bid through, and in particular past the politicians, was critical to News Corporation and News International.

In these matters, words count. Remember that Vince Cable lost his power to take the decision on the Sky bid after he was secretly recorded by Daily Telegraph reporters saying that he had "declared war on Murdoch". We are unlikely to ever find out what was said by Cameron and whoever he was talking to, but the suggestion that discussions took place raises uncomfortable questions.

At her select committee hearing, Brooks was at pains to point out she had not just her friendship with the prime minister to further Murdoch's causes, telling MPs on the culture media and sport committee that "there is just a lot out there that just isn't true particularly around my relationship with David Cameron. The truth is he is a neighbour and a friend. I deem the relationship to bewholly appropriate and at no time have I had any conversation with the prime minister that you in the room would disapprove of."

Nevertheless, there remains an important layer of protection for Cameron. If Cameron was lobbied by News International executives over the Sky deal, then it also has to be asked if the prime minister sought to discuss the Sky bid with Hunt. When the subject was touched on, earlier in the Commons debate, Hunt, sitting on the front bench near the prime minister, vigorously shook his head.

That said, Cameron will be wise to clarify, because gestures in this area are not enough. What conversation did he have regarding BSkyB? When was it, and who was it with? Did he tell O'Donnell, when the cabinet secretary gave him a clean bill of health? With relations between the Murdochs, Brooks and Cameron in such intense focus, the prime minister needs to be incredibly transparent about his role in the Sky bid – and dismiss any concerns that there was some sort of behind-the-scenes lobbying to get the blockbuster media merger through.