LONDON — Prime Minister David Cameron called today for an emergency session of Parliament on the phone hacking and police bribery scandal as the spreading crisis forced two of Britain's top police officers to resign in less than 24 hours.

Scotland Yard chief Paul Stephenson stepped down Sunday night, followed out the door today by Assistant Commissioner John Yates. Yates was the official who decided two years ago not to reopen police inquiries into phone hacking, saying he did not believe there was any new evidence.

The high-profile resignations are making it harder for Cameron to contain the intensifying scandal that is threatening his leadership and knocking billions of Rupert Murdoch's global media empire.

Parliament was to break for the summer on Tuesday after lawmakers grilled Murdoch, his son James and Murdoch's former British chief executive Rebekah Brooks in a highly anticipated public airing about the scandal.

Cameron said “it may well be right to have Parliament meet on Wednesday so I can make a further statement.”

Cameron spoke in Pretoria, South Africa, on the first day of a two-day visit to Africa. He had planned a longer trip, but cut it short as his government faces a growing number of questions about its cozy relationship with the Murdoch empire and a scandal that has taken down top police and media figures with breathless speed.