London (CNN) -- Global media tycoon Rupert Murdoch spent hours Wednesday downplaying his political influence, even as British Prime Minister David Cameron said politicians in his country had been too close to Murdoch over the years.
Murdoch insisted that his newspapers did not lobby for his commercial interests and he had "never asked a prime minister for anything."
Murdoch was being grilled about his relationship with politicians at an independent British inquiry prompted by illegal eavesdropping by his News of the World newspaper.
Murdoch told the Leveson Inquiry he does not believe in journalists using phone hacking or private detectives, calling it "a lazy way of reporters doing their job."
The media baron, who owns the Sun and the Times in London, as well as controlling the Wall Street Journal, New York Post and Fox News, also denied using the power of his press for personal gain.
At the same time, Cameron was saying politicians from across the political spectrum had been too close to the powerful media baron.
"I think we all, on both sides of this house, did a bit too much cozying up to Mr. Murdoch," he told the House of Commons as his government was battered over testimony Murdoch's son had given the day before.
James Murdoch testified Tuesday that before Cameron became prime minister, he had met the politician over drinks at a pub and told him the company's Sun newspaper would support his Conservative party in the next election.
Meanwhile, Rupert Murdoch was having a bitter falling out with then-Prime Minister Gordon Brown, the elder Murdoch said Wednesday.
He told Brown his papers would not support Brown's Labour party in the 2010 election, prompting Brown to respond: "Your company has... declared war on my government and we have no alternative but to declare war on your company," Murdoch quoted Brown as saying.
"And I said, 'I'm sorry about that Gordon, thank you for calling.' End of subject," Rupert Murdoch said.
He earlier insisted strongly that there had been no quid pro quo with Tony Blair as Murdoch's papers switched support from the Conservative party to Blair's Labour party in 1997 -- not long before Blair swept into power as prime minister.
"I, in 10 years in his power there, never asked Tony Blair for any favors and never received any," Murdoch said, pounding his hand on the table for emphasis.
On Tuesday, Leveson Inquiry lawyer Robert Jay pressed James Murdoch over the extent of his contact with politicians as the company moved to take full ownership of satellite broadcaster BSkyB.
That bid that collapsed because of the phone-hacking scandal.
Evidence published Tuesday suggests that News Corp. was getting inside information from the office of the government minister with the power to approve or block the acquisition, Culture Secretary Jeremy Hunt.
Adam Smith, an aide to Hunt, resigned Wednesday, saying his contacts with Murdoch representatives had gone beyond what the culture secretary had authorized.
But Hunt told the House of Commons he would not quit.
E-mails released by Leveson Inquiry "have been alleged to indicate there was a back channel through which News Corp. were able to influence my decisions. This is categorically not the case," Hunt said.
James Murdoch insisted before the Leveson Inquiry Tuesday that he knew little about the scale of phone hacking by people working for the News of the World, as he continued his fight to limit the damage the scandal does to him and his family's media empire.
The scandal has led to dozens of arrests on suspicion of criminal activity and forced News Corp. to pay hundreds of thousands of pounds in compensation to the victims of phone hacking.
James and Rupert Murdoch have been hammered over the past year about what they knew about phone hacking by people working for them.
Underlings did not tell James Murdoch how pervasive the practice was when he took over News Corp.'s British newspaper publishing arm, he testified Tuesday.
He agreed with a suggestion that the reason was because they knew he would put a stop to it.
"I think that must be it, that I would say, 'Cut out the cancer,' and there was some desire to not do that," he told the Leveson Inquiry.
Former Murdoch employees testified earlier that they told him about the problem.
The younger Murdoch has already been called twice to testify before British lawmakers and resigned from a number of top management positions at British subsidiaries of his father's media empire.
He and his father have always denied knowing about the scale of phone hacking, which police say could have affected thousands of people, ranging from celebrities and politicians to crime victims and war veterans.
Dozens of people have been arrested in criminal investigations into phone and e-mail hacking and police bribery, and police asked prosecutors last week to charge at least eight people.
The suspects include at least one journalist and a police officer, the Crown Prosecution Service said, declining to name them.
No charges have been filed, and the Crown Prosecution Service said it did not know when a decision would be made about charges.
In addition to the Leveson Inquiry and London's Metropolitan Police, two parliamentary committees also are looking into media conduct.
News Corp. shut down The News of the World, its British Sunday tabloid, last summer after public outrage at the scale of illegal eavesdropping its journalists did in search of stories.
CNN's Dan Rivers, Erin McLaughlin, Elaine Ly and Claudia Rebaza contributed to this report.