David Cameron is under pressure to appear before MPs on Monday to face Labour allegations that he is failing to take action on breaches of the ministerial code by Culture Secretary Jeremy Hunt.
Labour will demand that the Prime Minister comes before the Commons to make a statement as the row over the coalition's relations with Rupert Murdoch's News Corporation continues.
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. He said: "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."
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 accused Mr Hunt of having misled Parliament when he told the Commons last year he was releasing "all the documents relating to all the meetings, all the consultation documents, all the submissions we received, all the exchanges between my department and News Corporation".
Last week a raft of emails between Rupert Murdoch's company and Mr Hunt's office came to light for the first time - exposing the Culture Secretary to damaging allegations that he supported News Corporation's bid when he was supposed to be impartial.
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."