LONDON - Starting four days of testimony about the sway of Rupert Murdoch’s newspapers over public life here, Gordon Brown, the former prime minister, on Monday denied Murdoch’s depiction of some of the most contentious exchanges between the two men and accused a Murdoch newspaper, The Sun, of undermining Britain’s war effort in Afghanistan.

He also rejected assertions by a former editor of The Sun that Brown’s wife, Sarah, had approved a story in 2006 on the medical condition of the Browns’ infant child, who had been diagnosed at 4 months of age with cystic fibrosis.

Gordon Brown said The Sun caused “huge damage to the war effort’’ in Afghanistan, where British troops have been the main allies of US forces in the international coalition, by publishing stories suggesting that his government, in office from 2007 to 2010, “didn’t care about our troops.’’

He referred specifically to a story in 2009 disclosing that Brown had misspelled the name of a British soldier killed in Afghanistan. Brown also cited some aspects of what he called The Sun’s campaign over Afghanistan.

“The whole focus of their coverage was not what we had done,’’ he said, “but that I personally did not care about our troops.’’

Brown said Murdoch told him in a private letter that he disagreed with Britain’s “management of the war effort.’’ In response to Brown’s allegations, a spokeswoman for Murdoch’s News Corp., based in New York, said Murdoch “stands by his testimony.’’

The former prime minister was the first in a series of past and present political heavyweights to appear this week before the judicial inquiry led by Lord Justice Brian Leveson into the phone hacking scandal that exploded over Murdoch’s British tabloids last summer.

As the inquiry has inched forward, so, too, has a parallel police investigation in which around 50 people have been arrested, accused of making or allowing illicit phone intercepts, bribery of public officials, mainly the police, and e-mail hacking.

Britain’s Crown Prosecution Service said Monday that it had received files from the police relating to five unidentified journalists in the phone hacking investigation to assess whether they should face criminal charges. The prosecution service declined to provide further details.

Brown’s testimony, delivered in his hallmark Scottish burr, seemed among the most forthright in contradicting sworn testimony by Murdoch and by Rebekah Brooks, a former editor of The Sun who became chief executive of News International, the British newspaper subsidiary of Murdoch’s News Corp. She resigned as the hacking scandal broke in July.

The four days of hearings will culminate Thursday with a daylong appearance by Prime Minister David Cameron of Britain. Another former prime minister, Sir John Major of the Conservative Party, is to testify Tuesday.

Brooks has testified to the Leveson inquiry that Sarah Brown gave permission for the article on their son to be published, but the former prime minister denied that.

“I don’t think any child’s medical information should be broadcast,’’ he said. “There was no question ever of implicit or explicit permission.’’

Rather, he said, he and his wife had been presented with a “fait accompli’’ that the story was to be published.

In messages on Twitter, journalists at The Sun rejected Gordon Brown’s version of events both relating to the newspaper’s Afghanistan coverage and about the newspaper’s source for the article on his son.

Robert Jay, the inquiry’s lead counsel, also pressed Brown about a conversation with Murdoch in which Murdoch testified that the former prime minister threatened to “make war’’ on Murdoch companies after their tabloids had switched to the Conservatives in late 2009.

In April, Murdoch told the Leveson inquiry that Brown had said, “Well, your company has declared war on my government and we have no alternative but to make war on your company.’’ Murdoch also said Brown did not seem to be in “a very balanced state of mind.’’

“This conversation never took place,’’ Brown said. “I’m shocked, surprised, that it should be suggested.’’

He added later: “This call did not happen. This threat was not made.’’