LONDON (AP) — Scotland Yard’s assistant commissioner resigned Monday, a day after his boss also quit, and fresh investigations of possible police wrongdoing were launched in the phone hacking scandal that has spread from Rupert Murdoch’s media empire to the British prime minister’s office.

Prime Minister David Cameron called an emergency session of Parliament on the scandal and cut short his visit to Africa to try to contain the widening crisis. Lawmakers on Tuesday are to question Murdoch, his son James and Rebekah Brooks, the former chief executive of Murdoch’s U.K. newspaper arm.

In a further twist, a former News of the World reporter who helped blow the whistle on the scandal was found dead Monday in his home, but it was not believed to be suspicious.

Murdoch shut down the News of the World tabloid after it was accused of hacking into the voice mail of celebrities, politicians, other journalists and even murder victims.

The crisis has roiled the upper ranks of Britain’s police, with Monday’s resignation of Assistant Commissioner John Yates — Scotland Yard’s top anti-terrorist officer — following that on Sunday of police chief Paul Stephenson over their links to Neil Wallis, an arrested former executive from Murdoch’s shuttered News of the World tabloid whom police had employed as a media consultant.

The government quickly announced an inquiry into police-media relations and possible corruption.

Home Secretary Theresa May said that people were naturally asking “who polices the police,” and announced an inquiry into “instances of undue influence, inappropriate contractual arrangements and other abuses of power in police relationships with the media and other parties.”

The Independent Police Complaints Commission also said it was looking into the claims, including one that Yates inappropriately helped get a job for Wallis’ daughter. Wallis, former executive editor of News of the World, was arrested on suspicion of conspiring to intercept communications.

Yates said he had done nothing wrong.

“I have acted with complete integrity,” he said. “My conscience is clear.”

In another development, police confirmed that a second former News of the World employee was employed by Scotland Yard. Alex Marunchak had been employed as a Ukrainian language interpreter with access to highly sensitive police information between 1980 and 2000, the Metropolitan Police said.

Scotland Yard said it recognized “that this may cause concern and that some professions may be incompatible with the role of an interpreter,” adding that the matter will be looked into.

The prime minister is under heavy pressure after the resignations of Stephenson and Yates, and Sunday’s arrest of Brooks — a friend and neighbor whom he has met at least six times since entering office 14 months ago — on suspicion of hacking into the cellphones of newsmakers and bribing police for information.

Cameron’s critics grew louder in London as he visited South Africa on a two-day visit to the continent already cut short by the crisis. He dropped stops in Rwanda and South Sudan as his government faces growing questions about its cozy relationship with Murdoch’s media empire during a scandal that has taken down top police and media figures with breathtaking speed.

Parliament was to break for the summer on Tuesday after lawmakers grilled Murdoch, his son James and Brooks, in a highly anticipated public airing about the scandal. Cameron, however, said lawmakers should reconvene Wednesday “so I can make a further statement.”

Cameron insisted his Conservative-led government had “taken very decisive action” by setting up a judge-led inquiry into the wrongdoing at Murdoch’s now-defunct tabloid News of the World and into the overall relations between British politicians, the media and police.

“We have helped to ensure a large and properly resourced police investigation that can get to the bottom of what happened, and wrongdoing, and we have pretty much demonstrated complete transparency in terms of media contact,” Cameron said.

Opposition leader Ed Miliband, however, said Cameron needed to answer “a whole series of questions” about his relationships with Brooks, James Murdoch and Andy Coulson, the former News of the World editor whom Cameron later hired as his communications chief. Coulson resigned that post in January and was arrested earlier this month in the scandal.

“At the moment, he seems unable to provide the leadership the country needs,” Miliband said of Cameron.

Rupert Murdoch, too, faces a major test Tuesday in his bid to tame a scandal that has already destroyed the News of the World, prompted the resignations of Brooks and Wall Street Journal publisher Les Hinton, and sunk the media baron’s dream of taking full control of a lucrative satellite broadcaster, British Sky Broadcasting.

At the televised hearing, politicians will seek more details about the scale of criminality at the News of the World. The Murdochs will try to avoid incriminating themselves or doing more harm to their business without misleading Parliament, which is a crime.

Meanwhile, Internet hackers took aim at Murdoch late Monday, defacing the website of his other U.K. tabloid, The Sun, and shutting down The Times of London.

Visitors to The Sun website were redirected to a page featuring a story saying Murdoch’s dead body had been found in his garden.

Internet hacking collective Lulz Security took responsibility for that hacking attack via Twitter, calling it a successful part of “Murdoch Meltdown Monday.”

The group posted taunting messages on its Twitter account like “we have joy we have fun we have messed up murdoch’s sun.” It added what it claimed were details of hacked internal staff data from The Sun and eventually redirected the paper’s website to its own Twitter feed.

Lulz Security, which has previously claimed hacks on major entertainment companies, FBI partner organizations and the CIA, hinted that more was yet to come, saying “This is only the beginning.”

It later took credit for shutting down News International’s corporate website.

Another hacking collective known as Anonymous claimed the cyberattack on The Times’ website.

The website breaches came just hours ahead of Murdoch’s testimony to British lawmakers and as James Murdoch — chairman of BSkyB and chief executive of his father’s European and Asian operations — appeared increasingly isolated following the departure of Brooks.

James Murdoch did not directly oversee the News of the World, but he approved payments to some of the paper’s most prominent hacking victims, including 700,000 pounds ($1.1 million) to Professional Footballers’ Association chief Gordon Taylor.

James Murdoch said last week that he “did not have a complete picture” when he approved the payouts.

Rupert Murdoch is eager to stop the crisis from spreading to the United States, where many of his most lucrative assets — including the Fox TV network, 20th Century Fox film studio, The Wall Street Journal and the New York Post — are based.

News Corp. on Monday appointed commercial lawyer Anthony Grabiner to run its Management and Standards Committee, which will deal with the phone hacking scandal. It said the committee will cooperate with all investigations on hacking and alleged police payments, and carry out its own inquiries.

Meanwhile, one of the first voices to blow the whistle on the phone hacking — former News of the World journalist Sean Hoare — was found dead Monday in Watford, about 25 miles (40 kilometers) northwest of London. Police said the death was being treated as unexplained but was not considered suspicious, according to Britain’s Press Association.

Hoare was quoted by The New York Times saying that phone hacking was widely used and even encouraged at the News of the World under Coulson.