David Cameron has been dramatically summoned to explain to MPs why he has not ordered a probe into Culture Secretary Jeremy Hunt.
Commons Speaker John Bercow approved an urgent question tabled by Labour demanding to know why the issue of Mr Hunt's links to News Corporation has not been handed to independent adviser on ministerial interests Sir Alex Allan.
Downing Street confirmed that the Prime Minister - who had been due to visit Milton Keynes campaigning for local elections - will respond personally in the Commons.
On Sunday, Mr Cameron offered qualified support to his Cabinet minister, who is facing calls to resign over his handling of the BSkyB deal.
The premier insisted he did not currently believe the ministerial code had been broken - although he also hinted that an independent investigation could take place after Mr Hunt has given evidence to the Leveson Inquiry.
He also said Mr Hunt's special adviser Adam Smith had been right to resign over "too close, too frequent" contacts with News Corp lobbyist Frederic Michel.
But on Monday morning, Labour leader Ed Miliband sought to broaden the controversy by saying it "goes to the character of the Government".
The decision by Mr Bercow could fuel tensions with Number 10, amid sniping about bias and grandstanding.
Labour believes it is the first time a prime minister has been summoned to the House since urgent questions were introduced a decade ago.
A senior party source said: "He should have not been dragged. He should be doing the right thing."