The government has been under pressure over its closeness to Murdoch's News Corporation after Murdoch and his son James gave evidence under oath last week at the British inquiry into press ethics.
Cameron openly admitted courting newspaper proprietors to get his point of view across and that the relationship between politicians and the press had become too close.
But he maintained there was no agreement that in return for the support of his newspapers, among them The Sun and The Times, he would help Murdoch's business interests, including his now-dropped bid for full control of pay-television giant BSkyB.
"The thing that people are asking is: was there some big deal, some big agreement between me and Rupert Murdoch or James Murdoch that in return for their support for the Conservative Party I would somehow help their business interests or allow this merger to go through. That is not true," he said.
"I do not do things to change my policies to suit this proprietor or that proprietor. That is not the way I work and I will say that under oath," he told BBC television.
"It would be absolutely wrong for there to be any sort of deal -- and there wasn't."