Business Secretary Vince Cable has told how he rejected approaches by News Corporation to meet and discuss its attempts to take over BSkyB.
Giving evidence to the Leveson Inquiry, Mr Cable said he considered that a meeting with James Murdoch would have been "inappropriate".
He also told the probe into media ethics that he believed the Murdochs have a "disproportionate influence" on politicians and that the leaders of political parties had become too close to them.
In his written evidence , he said there was a "sense of being under siege from a well-organised operation" while he was handling the BSkyB bid.
He said the only conversation he had with anyone at News Corp was with James Murdoch on June 15 2010 when he called to say the bid was about to be announced.
He was invited to a News International drinks the next day but decided it would not be appropriate to go.
News Corp lobbyist Frederic Michel also contacted his office "on a number of occasions" but he refused to meet him after taking advice.
Mr Cable denied that he had met with other parties who were interested in preventing the acquisition and said he had instructed everyone to put their case in writing.
In his statement, he also explained his comment to undercover reporters in December 2010 that he would "declare war" against Rupert Murdoch.
This led to the Cabinet minister being stripped of his role in the quasi-judicial process looking at the takeover bid, which was then given to Culture Secretary Jeremy Hunt .
Mr Cable said the declaration was an attempt to show that he could not be influenced or intimidated by News Corp.
Lib Dem colleagues had expressed alarm that the affair could lead to "retribution" against the party via News International's newspapers, he explained.
"My references to 'War on Murdoch' were making the point, no doubt rather hyperbolically, that I had no intention of being intimidated," his statement said.
"Clearly I should not have volunteered my unprompted opinion, even in a private, confidential conversation in a constituency surgery, I subsequently apologised."
Mr Cable also told the inquiry that politicians could still think independently even if they had their own views and opinions on issues they were having to handle.
"With an independent mind doesn't mean with a blank mind. Most people in public life have views, opinions," he said.
"Probably, if they are politicians, those views and opinions have been on the record and the requirement on me and people in this position is to set those on one side for the sake of making this decision, to consider representations, the evidence, the facts - and decide on that and only on that."
The Cabinet Minister said he followed the maxim: "If you can't ride two horses at once you shouldn't be in the circus."
He insisted his handling of the takeover bid had been conducted entirely fairly.
He said: "All the decisions in the department were subject to advice from officials (and) departmental lawyers, because they were conscious that if a decision was made with bias or perceived bias then legal action could be taken, in this case through the Competition Appeals Tribunal - equivalent to a judicial review."
News Corp had wanted to buy the remaining 39% of BSkyB, which owns Sky News, that it does not already hold but abandoned the bid last summer after the phone hacking row escalated.