Metropolitan Police Assistant Commissioner John Yates became the second senior officer to quit in two days over the phone-hacking scandal at News Corp.’s News of the World newspaper in the U.K.

Yates, Britain’s top anti-terrorism policeman, announced his resignation in a statement e-mailed today by the force. It follows the departure of Commissioner Paul Stephenson announced yesterday and means London is losing two of its top police officers a year before the capital hosts the Olympics.

“In both cases the right call was made,” London Mayor Boris Johnson said in a televised news conference. “We have to recognize that the nexus of questions about the relationship between the Met and the News of the World was likely to be distracting to both officers in the run-up to the Olympic Games.”

The police are facing mounting pressure over their handling of the probe into phone-hacking by reporters at the now defunct News of the World tabloid. Last week, they arrested Neil Wallis, a former deputy editor, on suspicion of conspiring to intercept phone calls. Wallis worked as a paid communications consultant for the police in 2009 and 2010.

At a parliamentary hearing on March 24, Yates said he may have met Wallis for lunch or dinner in February, the month after police began the latest inquiry into phone-hacking.

‘Complete Integrity’

The Independent Police Complaints Commission today said in a statement on its website that it has been asked to probe the conduct of Stephenson and Yates and two unnamed “former senior officers” for their roles in the phone-hacking investigation.

Yates said in an e-mailed statement that he had acted with “complete integrity” and that his conscience was clear. “Those of us who take on the most difficult jobs clearly have to stand up and be counted when things go wrong,” he said. “It is a matter of great personal regret that those potentially affected by phone hacking were not dealt with appropriately.”

Johnson said Yates resigned after being told he would be suspended. He will be replaced as head of anti-terror operations by another assistant commissioner, Cressida Dick, who in 2009 became the first woman to hold that rank.

A trained hostage negotiator and policewoman since 1983, Dick was also the officer who was in charge on July 22, 2005, when police killed Jean Charles de Menezes, a Brazilian electrician who was mistaken for a suicide bomber.

Continuity

Prime Minister David Cameron and Home Secretary Theresa May sought to reassure the public by promising continuity in the force in tackling counter-terrorism in the capital and the U.K.

“What matters now is that we ensure swift and effective continuity at the Metropolitan Police Service,” Cameron said in a statement in Johannesburg, where he is on a visit.

Opposition Labour Party leader Ed Miliband said earlier today that there was a “a big cloud” over Yates, while former Deputy Prime Minister John Prescott said the officer shouldn’t remain in the job. Johnson earlier told BBC Radio 4 that there were “questions” over Yates’s relationship with Wallis.

Yates’s resignation increases the pressure on Cameron over his own decision to hire former News of the World editor Andy Coulson as his communications chief in 2007.

In his resignation statement yesterday, Stephenson raised the question of why it was wrong for him to have worked with Wallis, yet right for Cameron to have hired Coulson, who was Wallis’s boss at the News of the World. Coulson resigned from his government job in January as allegations of wrongdoing at the paper mounted and was arrested July 8.

‘Swift’ Departure

Speaking to lawmakers in Parliament today, May said she hopes Stephenson will “leave his post as swiftly as possible” and that his deputy Tim Goodwin, who filled in for Stephenson when he was on sick leave, will take over as acting commissioner.

News of the World reporter Clive Goodman and private investigator Glenn Mulcaire were jailed in 2007 for intercepting phone messages left for members of Prince Charles’ staff. At the time, police said there were no grounds to arrest anyone else in relation to phone-hacking at the tabloid. Yates reviewed the case in 2009 and ruled out the need for further inquiry.

Since then, dozens of victims of phone-hacking have been identified, including the actress Sienna Miller, sports commentator Andy Gray and a murdered schoolgirl, Milly Dowler. Cameron told lawmakers last week police are now looking through 11,000 pages of evidence containing 3,870 names, including about 4,000 mobile and 5,000 landline phone numbers.

‘Poor’ Decision

Yates appeared last week before Parliament’s Home Affairs Committee. Lawmakers laughed at him as he said the decision not to investigate further, taken after an eight-hour review, had been “poor.”

“You just don’t seem like the dogged and determined sleuth we would expect,” said Steve McCabe, an opposition Labour Party lawmaker. Committee Chairman Keith Vaz told him his testimony had been “unconvincing.”

Yates will appear before the home affairs committee again tomorrow, alongside Stephenson and Dick Fedorcio, director of public affairs for the police.

Since the July 4 revelation that reporters working for the News of the World hacked Dowler’s mobile phone and deleted messages, what Cameron called a “firestorm” has swept through the British media, the political world and the police.

Scandal

In two weeks, the scandal has forced News Corp. Chairman Rupert Murdoch to close the 168-year old tabloid, abandon a bid to take control of British Sky Broadcasting Group Plc (BSY) and accept the resignations of News International Chief Executive Officer Rebekah Brooks and Les Hinton, the U.S.-based CEO of Dow Jones and previously chairman of News International for 12 years.

Yates handled a series of high-profile and controversial cases in his career. He ran the cash-for-honors inquiry into whether Prime Minister Tony Blair’s government had sold seats in the House of Lords. That probe, which ran from 2006-7, was the most serious ever to involve a British prime minister. Blair himself was questioned three times, and one of his staff was arrested in a dawn raid. No one was charged.

In 2002, Yates was criticized after the collapse of the trial of Paul Burrell, Princess Diana’s butler, for stealing some of her possessions. Yates had led the probe. He was awarded the Queen’s Police Medal in 2005 for his work handling the police response to the 2004 Asian tsunami.

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