Updated

Security preparations for the 2012 Olympics won't be affected by the resignations of London's top two police officers, the British government said Monday.

Scotland Yard chief Paul Stephenson and Assistant Commissioner John Yates, Britain's top anti-terrorist officer, have resigned amid an intensifying scandal involving phone hacking and alleged police bribery.

Both indicated that they quit to ensure the police force had stable leadership and no distractions in the run-up to the first Olympics in London since 1948, which have a $1.2 billion security budget.

Olympics minister Hugh Robertson insisted that much of the security framework was already in place before counterterrorism minister Pauline Neville-Jones left her job in May .

"I am not concerned about the resignations in relation to Olympics security," Robertson said Monday in statement to The Associated Press. "Pauline Neville-Jones made a massive contribution to get this in a good place. The appointment of Chris Allison, as the Met assistant commissioner in charge of all of this, has also really driven it forward. He is the point man on Olympic security and I am 100 percent confident that we are where we ought to be."

Jonathan Evans, the director of domestic spy agency MI5, has said the Olympics "represent a significant target for terrorist groups."

London was hit by terrorists the day after London was awarded the Olympics in July 2005, with homegrown suicide bombers attacking the transit network and killing 52 commuters.

Britain is planning for the terror threat to be "severe" during the Olympics, meaning an attack is highly likely, despite the national level being downgraded by the government last week.

"Our enemies have clearly said the Olympics will be attacked in the same way that they said that Heathrow (Airport) and the tube (underground) would be attacked," Conservative lawmaker Patrick Mercer, a former head of the British Parliament's counterterrorism subcommittee, told the AP. "The reason we haven't had any serious terrorist activity since 2005 is because of the efficiencies of our security forces generally — much of which is to do with the police."

Mercer said Stephenson and Yates will be "extremely difficult to replace, if not impossible."

"It's not long to the Olympics," Mercer said. "A decision (on Stephenson's successor) needs to be taken efficiently, quickly and absolutely dispassionately."

Security has always been a critical concern for the Olympics since the killing of 11 Israeli athletes and coaches at the 1972 Munich Games.

About 12,000 police officers will be on duty each day of the July 27-Aug. 12 games.

The centerpiece complex is the 1-square-mile Olympic Park in the Stratford area, where venues include the 80,000-seat main stadium. Up to 250,000 spectators a day are expected to flood into the park during the games.

"It's not ideal that you've had your senior officers resigning a year before the Olympics," said Tobias Feakin, the Royal United Services Institute's director for national security and resilience. "There's no doubting it's a knock, but there's a huge amount of planning already in place."