Labour MP Tom Watson, one of News International's chief critics in Parliament, has described James Murdoch's evidence as "fascinating".
"I think what will probably concern parliamentarians from this morning's session is the degree of contact between special advisers and executives at the company," he told BBC Radio 4's The World At One.
Watson said the December 2010 conversation between Cameron and Murdoch would "raise some eyebrows" among civil servants.
"They would normally want to protect the Prime Minister and make sure he had a witness with him when those conversations took place," he said.
"The fact that they actually discussed the bid - he should just have come clean about that earlier on."
Watson said the Culture, Media and Sport Select Committee was "hoping" to make its conclusions, following its own inquiry into phone hacking, next week.
Murdoch said at News Corp they were "alive to the risk that politics or commercial interest" might inflict on the deal, but rested on "the soundness of the legal case".
The inquiry heard there were a number of meetings between News Corp representatives, including Murdoch, and various Government figures, including Cable and Culture Secretary Jeremy Hunt, during the company's offer for BSkyB.
Tom Watson has described Murdoch's testimony as "fascinating"
Murdoch and Rebekah Brooks met Tory MP Oliver Letwin in July 2009, and he met Jeremy Hunt in October 2009 and February 2010 when they discussed issues relating to the media including piracy, broadband, Ofcom, and media regulation.
But he told the hearing the company had not gained any advantage from its communications with politicians, although there may have been a perception by politicians that support from a newspaper like The Sun would help them.
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The inquiry heard that consultation was being carried out on the bid which was due to finish on 8 July 2011 - but on 4 July that year the Guardian published its story about Milly Dowler's phone being hacked. It eventually prompted News Corp to withdraw the bid.
The hearing was shown emails between Frederic Michel, News Corp's director of public affairs, and Murdoch.
In one, Mr Michel said he had been told by one of Mr Hunt's advisers that it was likely the Government would be "supportive throughout the process".
The inquiry also heard that, after a blog entry by BBC News business editor Robert Peston in September 2010 saying Ofcom was expected to review the bid, within minutes the company had contacted the Department for Culture, Media and Sport to find out more information.
But Murdoch said he would never expect News Corp's support for politicians to help the firm's interests.
"That is absolutely not the case and the question of support of an individual newspaper for politicians one way or another is not something that I would ever link to a commercial transaction like this," he said.
"Nor would I expect that political support one way or another ever to translate into a minister behaving in an appropriate way, ever.
"I simply would not do business that way."
QC Mr Jay asked Murdoch about a comment, apparently from Hunt's website, that said: "Like all good Conservatives, Hunt is a cheerleader for Rupert Murdoch's contribution to British television."
But Murdoch denied the Culture Secretary was a "huge ally", saying: "I wouldn't describe it that way. I don't think so."
During Murdoch's evidence, the hashtag#helpjamesmurdoch began trending on Twitter.
Earlier, Murdoch admitted that the News of the World should not have run the Max Mosley "Sick Nazi Orgy" story, which led to the former Formula 1 boss receiving more than £60,000 in compensation.