Media playback is unsupported on your device Media caption David Cameron: "I am extremely sorry I employed him. It was the wrong decision and I am clear about that."

Prime Minister David Cameron has apologised for employing Andy Coulson as his director of communications.

"I am extremely sorry I employed him. It was the wrong decision," he said.

He spoke after the ex-News of the World editor was found guilty at the Old Bailey of conspiring to hack phones between 2000 and 2006.

Labour leader Ed Miliband said: "This isn't just a serious error of judgement, it taints David Cameron's government."

Mr Cameron appointed Coulson as his media chief in July 2007 - six months after he had quit as NoW editor on the day the paper's former royal editor was jailed for four months for phone hacking.

Coulson said he took "ultimate responsibility" for that scandal, even though he maintained he was unaware of any phone hacking by his journalists.

Mr Cameron took Coulson into Downing Street after becoming PM in 2010, only for him to resign in 2011 amid growing allegations about phone hacking during his time as editor.

'Assurances'

In a statement to the media after Tuesday's verdicts, Mr Cameron said he took "full responsibility for employing Andy Coulson".

Image copyright Rex Features

"I did so on the basis of undertakings I was given by him about phone hacking and those turn out not be the case.

"I always said if they turned out to be wrong, I would make a full and frank apology and I do that today. I am extremely sorry that I employed him. It was the wrong decision."

Asked what checks he had made before employing Coulson, he said: "I asked him questions, if he knew about phone hacking, and he said he didn't and I accepted those assurances and I gave him the job.

"I would say that no one has made any complaints about the work that he did for me, either as leader of the opposition or here, in Number 10 Downing Street. But knowing what I now know and knowing those assurances weren't right, it was obviously wrong to employ him.

"I gave someone a second chance and it turned out to be a bad decision."

Analysis - BBC political editor Nick Robinson

Coulson was seen as a huge catch when he was first hired to be David Cameron's spin doctor. He was the former editor of the country's biggest selling newspaper and a man with close connections to Rupert Murdoch - the most powerful media mogul in Britain.

As for allegations about phone hacking at the News of the World they were all in the past - weren't they?

Again and again Cameron parried questions about hiring Coulson by saying that he deserved a second chance.

But the evidence mounted of what had happened at the paper he'd once edited. After 168 years the News of the World came to a tearful end and the police arrested the former Director of Communications at Number 10.

The prime minister was forced to change his defence of the man he called his friend. Tonight a man who helped get his boss into Number 10 faces up to a new life - in prison. His former boss faces serious questions about his judgement.

Labour leader Ed Miliband said Mr Cameron had "brought a criminal into the heart of Downing Street", adding that he "must have had his suspicions about Mr Coulson and yet he refused to act".

"We now know that he put his relationship with Rupert Murdoch ahead of doing the right thing when it came to Andy Coulson," said the Labour leader.

He said the prime minster needed to do more than apologise - he "owes the country an explanation" as to why he did not act after the allegations surfaced.