LONDON — Starting four days of evidence by political leaders about the sway of Rupert Murdoch's newspapers over public life here, former Prime Minister Gordon Brown on Monday denied Mr. Murdoch's depiction of some of their most contentious exchanges and accused a leading Murdoch newspaper, The Sun, of undermining Britain's war effort in Afghanistan.
He also rejected assertions by a former editor of The Sun that Mr. Brown's wife, Sarah, had approved a story in 2006 on the medical condition of the Browns' infant child, who had been diagnosed at four months with cystic fibrosis.
Mr. Brown said The Sun caused "huge damage to the war effort" in Afghanistan, where British troops have been the main allies of American 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 Mr. Brown had misspelled the name of a British soldier killed in Afghanistan and aspects of what he called a "campaign" by The Sun 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."
Mr. Brown said that Mr. Murdoch told him in a private letter that he disagreed with Britain's "management of the war effort." In response to Mr. Brown's allegations, a spokeswoman for Mr. Murdoch's News Corporation, based in New York, said Mr. 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 Leveson into the phone hacking scandal that exploded over Mr. 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 in connection with 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 file 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.
Mr. Brown's testimony, delivered in his hallmark Scottish burr, seemed among the most forthright in contradicting sworn testimony by Mr. Murdoch and by Rebekah Brooks, a former editor of The Sun who became chief executive of News International, the British newspaper subsidiary of Mr. Murdoch's News Corporation. She resigned as the hacking scandal broke last July.
Ms. Brooks has testified to the Leveson inquiry that Mr. Brown's wife, Sarah, 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 Mr. 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.
In her own testimony to the inquiry, Ms. Brooks said the article came from the father of another child with cystic fibrosis.
Scottish health authorities who dealt with the case said in a statement on Monday that, while there had been "no inappropriate access to the child's medical records," it was "highly likely" that a local employee "spoke, without authorization, about the medical condition of Mr. Brown's son, Fraser."
In a statement, News International said it welcomed the fact that Scottish authorities "said that they believe there was 'no inappropriate access' to the medical records of Gordon Brown's son." The Sun stood by its previous rejection of Mr. Brown's complaints, the statement said.
Robert Jay, the inquiry's lead counsel, also pressed Mr. Brown about a conversation with Mr. Murdoch in which Mr. 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, Mr. Murdoch told the Leveson inquiry that Mr. Brown had said, "Well, your company has declared war on my government and we have no alternative but to make war on your company." Mr. Murdoch also said that Mr. Brown did not seem to be in "a very balanced state of mind."
"This conversation never took place," Mr. Brown said. "I'm shocked, surprised, that it should be suggested." He added later: "This call did not happen. This threat was not made."
"I couldn't be unbalanced on a call that I didn't have," Mr. Brown said.
Mr. Brown said that, while he respected Mr. Murdoch's business acumen, he rejected suggestions that the tycoon had influenced his thinking. "The idea that I followed his views is absolute nonsense," Mr. Brown said.
The concentration of high-ranking figures at the inquiry this week has provoked speculation that the testimony could be among the most significant so far in the months-old investigation. George Osborne — the chancellor of the Exchequer and a close ally of Mr. Cameron — appeared before the inquiry after Mr. Brown completed three hours of testimony.
Mr. Osborne is seen as particularly close to Prime Minister Cameron from the days he took over the Conservative Party in opposition in 2005.
On Monday he acknowledged accompanying Mr. Cameron to a gathering, including Rupert Murdoch, at a chalet in the Swiss ski resort of Davos during the World Economic Forum in January 2009.
But much questioning centered on Mr. Osborne's role in the Conservatives' decision to hire Andy Coulson, a former editor of the now defunct News of the World, a Murdoch-owned Sunday tabloid, as director of communications.
The Conservatives hired Mr. Coulson after he was forced to resign as editor of The News of the World in 2007, in the early days of the hacking scandal before its full extent was widely known. His association with The News of the World also cost him his job as Mr. Cameron's director of communications after the Conservative victory at the 2010 election. Like Ms. Brooks, Mr. Coulson has been charged in recent weeks with criminal offenses.
"It was an issue that he had resigned at The News of the World," Mr. Osborne said, acknowledging that he had been aware of the hacking controversy that forced Mr. Coulson to resign his newspaper job. But Mr. Coulson assured him that the issue was resolved.
"I asked him in a general sense," Mr. Osborne said of Mr. Coulson, "whether there was more in the phone-hacking story that was going to come out that we needed to know about and he said, 'no'."
Mr. Osborne said he had believed Mr. Coulson to be a "good person for our shortlist" because of his "talent and ability" running a major newspaper and newsroom.
"If you were going simply on hiring someone who would not attract publicity, you would not have hired Mr. Coulson," he said. Mr. Osborne also said he had consulted Ms. Brooks about Mr. Coulson.
He said he asked here, "Tell me about Andy Coulson: is he a good person? Is he a good person to work with? I was simply asking for her opinion as him as a professional."
Mr. Murdoch's tabloids supported the Conservatives for many years, but switched to Labour before the 1997 election that brought Tony Blair to power. Mr. Blair testified before the inquiry in late May.
Shortly before the 2010 election, which produced a coalition led by Mr. Cameron and Nick Clegg, a Liberal Democrat, as junior partner, the Murdoch tabloids switched back to the Conservatives.
Mr. Osborne said the Conservatives had sought the endorsement of The Sun as "one of a range of things." But, he added, "I certainly think you can win an election without the endorsement of the Sun."
Mr. Osborne rejected any suggestion that he, the government, or the Conservative Party had supported News Corporation's $12 billion bid to take over the 60.9 percent of BSkyB, the British satellite broadcaster, that it did not own already. The company withdrew the bid last summer at the height of the phone hacking furor.
Far from wanting to help News Corp. secure approval for the takeover, Mr. Osborne said, he regarded the bid as "politically inconvenient" in that however it was resolved, someone would be angry. And he said that government lawyers had determined that it was perfectly appropriate for the government to hand over responsibility for the bid to Jeremy Hunt, the Culture Secretary, even though he was known to be sympathetic to News Corporation's position.
Mr. Jay, the inquiry lawyer, seemed skeptical about Mr. Osborne's assertion that "I didn't have a strong view on the merits or demerits of the issue.
"It's rather unusual for someone to have such a lack of interest in something everyone was talking about," Mr. Jay said. The four days of hearings will culminate on Thursday with a daylong appearance by Mr. Cameron. Another former prime minister, Sir John Major of the Conservative Party, is to testify on Tuesday. Other political luminaries to appear include the leader of the Labour opposition, Ed Miliband, Mr. Clegg, the deputy prime minister, and Scotland's first minister, Alex Salmond.
Sarah Lyall contributed reporting.