LONDON (REUTERS) - British Prime Minister David Cameron on Wednesday apologised to parliament for hiring Andy Coulson, his ex-media chief, after Coulson was found guilty of being part of a phone-hacking conspiracy.

"I take full responsibility for employing Andy Coulson, I did so on the basis of assurances that I received. I am sorry, this was the wrong decision," Mr Cameron told parliament.

But in heated exchanges, Ed Miliband, the leader of Britain's opposition Labour party, repeatedly called Mr Cameron's judgment into question saying he had wilfully ignored warnings about Coulson and did not have any answers to a series of questions about the scandal.

"Today we know that for four years the prime minister's hand picked closest adviser was a criminal and brought disgrace to Downing Street. We now also know that the prime minister wilfully ignored multiple warnings about him," said Mr Miliband. "The prime minister will always be remembered as being the first ever occupant of his office who brought a criminal into the heart of Downing Street," he said, referring to the British leader's office.

Mr Miliband has long questioned Mr Cameron's judgment over Coulson who resigned as editor of Rupert Murdoch's now defunct News of the World newspaper in 2007 when two of its employees were jailed for phone-hacking before Mr Cameron hired him.

A jury at London's Old Bailey court on Tuesday found Coulson, who ran Mr Cameron's media operations from 2007-2011, guilty of conspiring to intercept messages to break news about royalty, celebrities and victims of crime.

Less than two hours after the verdict on Tuesday, Mr Cameron issued what he called a "full and frank" apology, saying he had taken Coulson's assurances of innocence at the time at face value, something he now realised was a mistake.