Prime Minister David Cameron has apologised to the British Parliament for hiring former tabloid editor Andy Coulson, who has been convicted of phone hacking, but faced fresh embarrassment as the judge rebuked him for speaking out about the case.

Cameron said it had been the “wrong decision” to make the News of the World editor his media chief in 2007, though denied ignoring warnings about Coulson’s activities at the tabloid, which Rupert Murdoch shut down in disgrace in July 2011.

The eight-month phone-hacking trial came to an end as jurors were sent home without reaching a verdict on two further charges that Coulson faced relating to alleged payments to police officers.

The judge at the Old Bailey court reprimanded Cameron for making his first apology for Coulson’s appointment soon after Coulson was convicted for hacking on Tuesday, but before the bribery verdicts came.

Judge John Saunders said he had rejected a request by Coulson’s defence lawyers to halt proceedings on the basis that jurors might be influenced by the premier’s views, but added it did not mean he was not concerned about what had happened.

Cameron hired Coulson just months after he resigned as News of the World editor in 2007, soon after the jailing of the paper’s royal editor and a private investigator for hacking.

Coulson, 46, always denied knowing about the practice and the prime minister stuck by him for almost four years despite media reports to the contrary.

“I always said that if (Coulson’s) assurances turned out to be wrong I would apologise fully and frankly to this House of Commons and I do so today from this despatch box. This was the wrong decision,” Cameron told the House of Commons.

Opposition Labour leader Ed Miliband said the charge against Cameron was “not one of ignorance, but one of wilful negligence”.

The high-profile trial centred on the News of the World’s efforts to hack the phones of Britain’s royal family, politicians, celebrities and victims of crime.

In a dramatic conclusion to one of the most expensive cases in British criminal history, Coulson was found guilty, but his fellow former editor and one-time lover Rebekah Brooks was cleared of all charges.

Coulson will learn next week his sentence for hacking — which could be a jail term of up to two years — and also whether prosecutors will seek a retrial on the bribery claims.