LONDON – Prime Minister David Cameron on Friday said James Murdoch, scion of Rupert Murdoch’s media empire, should be recalled by Parliament to address allegations he misled lawmakers in his testimony on Britain’s phone hacking.

Further upping the pressure on Murdoch, 38, an opposition lawmaker called for a police investigation into whether Murdoch lied.

At issue is whether News Corp. executives knew of the widespread practice of phone hacking at their now defunct News of the World tabloid — which illegally accessed the phones of thousands of British citizens — and whether the executives tried to cover it up.

In another development, U.S. Justice Department prosecutors are preparing subpoenas as part of their inquiry into allegations that News Corp. employees sought to hack into the phones of victims of the Sept. 11 terrorist attacks and tried to bribe law enforcement officers for information, people familiar with the matter said Friday.

The subpoenas would seek information from the company related to the phone hacking scandal that has engulfed Rupert Murdoch’s British media operations, the people said. Murdoch is chairman and chief executive of News Corp., which is based in New York and has extensive U.S. operations.

It is unclear if or when subpoenas will be issued and specifically what information they would seek. The Wall Street Journal, which is owned by News Corp., first reported on the preparation of the subpoenas and said they still require approval by senior Justice Department officials.

On Tuesday, while testifying beside his father before a British select committee, James Murdoch denied having ever seen a key piece of evidence in the case that emerged in 2008 — an email suggesting phone hacking went as high as the tabloid’s chief correspondent.

But after two former News Corp. executives cast doubt on his assertion — saying they personally had shown the younger Murdoch the email in question — several British lawmakers insisted he should be recalled to address the discrepancy.

On Friday, Cameron, who himself is under pressure for his close ties to News Corp. executives arrested over the phone hacking scandal, echoed those calls.

“Clearly James Murdoch has got questions to answer in Parliament, and I’m sure that he will do that,” Cameron said. “News International has got some big issues to deal with and a mess to clear up.”

But Murdoch, in a statement, said, “I stand behind my testimony to the select committee.”

Contradictions to Murdoch’s testimony emerged Thursday when Colin Myler, former editor of the News of the World, and Tom Crone, the former legal director at the tabloid, issued a statement effectively claiming the younger Murdoch had lied.

The two claimed they showed Murdoch the email, which was included in sealed court documents in the settlement of a 2008 lawsuit brought by Gordon Taylor, the executive director of Britain’s professional soccer players union, whose phone was allegedly hacked by the News of the World. Taylor received more than a $1.3 million in an out-of-court settlement, which some lawmakers now allege amounted to hush money to keep a lid on the scandal.

Titled “For Neville,” the email mentioned a transcript of a hacked conversation allegedly prepared for Neville Thurlbeck, the paper’s chief correspondent. The email — which Murdoch insists he never saw — is considered by lawmakers to be among the strongest pieces of evidence indicating that illegal hacking was not an isolated case.

Murdoch and other News Corp. officials have maintained that until relatively recently, they believed News of the World’s hacking had been limited to one 2005 incident, in which Prince William’s phone messages were intercepted by the tabloid’s royal correspondent and a private investigator.

The suggestion Murdoch may have known about the email infuriated lawmakers. Tom Watson, a member of the opposition Labor Party who specifically asked Murdoch on Tuesday about the email, said Friday that he had now referred the question to investigators at Scotland Yard.

U.S. officials said last week that the FBI had opened a preliminary probe into the allegations involving the 9/11 victims, in an effort to determine if U.S. laws were broken.