David Cameron is under pressure to appear before MPs over Labour allegations that he is failing to take action on breaches of the ministerial code by Culture Secretary Jeremy Hunt.
Labour is demanding that the Prime Minister makes a Commons statement as the row over the coalition's relations with Rupert Murdoch's News Corporation continues.
On Sunday, Mr Cameron offered qualified support to Mr Hunt, who is facing calls for his resignation over his handling of the BSkyB deal.
"As things stand, I don't believe Jeremy Hunt broke the ministerial code," Mr Cameron said, but he added that he could yet order an independent investigation after the Culture Secretary has given evidence to the Leveson Inquiry.
He has been resisting demands to call in his independent adviser on ministerial interests, Sir Alex Allan, arguing that the issue should be left to Lord Justice Leveson.
"If evidence comes out through this exhaustive inquiry where you're giving evidence under oath - if he did breach the ministerial code, then clearly that's a different issue and I would act," he said.
The Prime Minister said Mr Hunt's special adviser, Adam Smith, had been right to resign over his contacts with News Corporation lobbyist Frederic Michel, which were "too close, too frequent". But he added: "I don't think it would be right in every circumstance if a special adviser gets something wrong to automatically sack the minister."
Labour leader Ed Miliband believes Mr Cameron is failing to enforce the ministerial code and must explain himself to MPs. A Labour source said: "David Cameron is still trying to hide behind the Leveson Inquiry. With Parliament breaking up on Tuesday, Mr Cameron must come to the Commons and explain to the British people why he is ducking his responsibilities to enforce the ministerial code."
Mr Cameron faces scrutiny of his own conduct too after he admitted discussing News Corporation's takeover bid for BSkyB with James Murdoch while the Government was deciding whether to approve it. The Prime Minister acknowledged his embarrassment at attending a party thrown by then News International chief executive Rebekah Brooks - where the conversation took place - and hinted that he regretted doing so in retrospect.
But he insisted there had been no "grand deal" with Rupert Murdoch's media empire to wave through the takeover in return for support from News International newspapers. "It would be absolutely wrong for there to be any sort of deal and there wasn't," he said. "There was no grand deal."