Culture Secretary Jeremy Hunt is fighting for his political life following claims that he secretly backed News Corporation's bid to take over satellite broadcaster BSkyB.
Labour leader Ed Miliband insisted the Tory Cabinet minister must resign, accusing him of "acting as a back-channel" for the Murdochs.
But Mr Hunt insisted he had conducted the process of deciding whether to green-light the deal with "scrupulous fairness" and requested an early date at the Leveson Inquiry into press standards so he could give his side of the story in formal evidence.
The row is set to intensify as Labour prepares to face down David Cameron over the allegations at Prime Minister's Questions.
Mr Cameron's own links to the Murdochs will also come under the spotlight following Tuesday's evidence from James Murdoch at the inquiry.
The News Corp executive revealed that he and the Prime Minister had briefly discussed the BSkyB bid in December 2010 - two days after Business Secretary Vince Cable was stripped of his decision-making power on the takeover. That was at a Christmas dinner hosted by News International chief executive Rebekah Brooks the PM attended on December 23 2010.
Mr Murdoch told the inquiry that he and Mr Cameron mentioned what had happened. "He reiterated what he had said publicly, which is that the behaviour had been unacceptable, and I imagine I expressed the hope that things would be dealt with in a way that was appropriate and judicial," he said. "It was a tiny conversation ahead of a dinner where all these people were there, so it wasn't really a discussion."
The inquiry released a 163-page dossier of emails detailing contacts between the Culture Secretary's office and a senior executive at News Corp.
Labour said the documents showed that Mr Hunt failed to fulfil his quasi-judicial role in relation to the proposed takeover, which he had promised to carry out in a "fair and even-handed" way. Mr Miliband said: "He should resign. He himself said that his duty was to be transparent, impartial and fair in the BSkyB takeover. But now we know that he was providing advice, guidance and privileged access to News Corporation. He was acting as a back-channel for the Murdochs."
Mr Hunt said: "Now is not a time for knee-jerk reactions. We've heard one side of the story today but some of the evidence reported meetings and conversations that simply didn't happen. Rather than jump on a political bandwagon, we need to hear what Lord Justice Leveson thinks after he's heard all the evidence. Let me be clear my number one priority was to give the public confidence in the integrity of process."