Mr Yates, who quit his job as assistant commissioner yesterday, said he saw the tabloid's former deputy editor "two or three times a year" as a friend and had been to his house to pick him up for a football match.

His comments came as departing Commissioner Sir Paul Stephenson said he regretted the Wallis appointment - and blamed Mr Yates for telling him two years ago that there was nothing new in the phone hacking allegations.

Mr Yates was also blamed by Scotland Yard PR chief Dick Fedorcio for giving the go-ahead for the appointment of Mr Wallis, who is now under arrest for alleged phone hacking, to a £1,000-a-day press office job with the Met.

Mr Yates hit back by saying that Mr Fedorcio was "over-egging the pudding" and should have carried out "due diligence" on Mr Wallis himself before taking him on.

The clashes came during a dramatic hearing of the Commons home affairs select committee on the scandal attended by Sir Paul, Mr Fedorcio and Mr Yates.

Asked about his links with Mr Wallis, Mr Yates replied: "I would see him two or three times a year - he's a friend. Don't get the impression we are bosom buddies going round to each other's houses. I do not go round his house on a regular basis. I think I have been round there once to pick him up for a football match."

On the decision to hire Mr Wallis, Mr Yates said that he had a phone conversation with the former deputy editor before his employment with the Met and "sought absolute assurance" that there was nothing "still being chased" by journalists over the phone hacking inquiries that could embarrass the Metropolitan Police.

He added: "We should not forget that Neil Wallis is still an innocent man."

In further evidence, Mr Yates said that the Met had offered to explain to David Cameron about the scope of the phone hacking investigation, but said that Ed Llewellyn, the Prime Minister's chief of staff, had "for whatever reason" chose not to inform Mr Cameron.

When asked why he didn't reopen the investigation into hacking in 2009, following new allegations in the Guardian, Mr Yates admitted that he had been wrong.

He said: "Why would we have done, with what we knew at the time?" He then said "we know now what we know now" and added: "God, I wish I'd done something different."

Sir Paul insisted he had had no idea that Mr Wallis might be linked to the phone hacking scandal.

In a defiant appearance before the committee two days after his resignation, Sir Paul said: "I am quite happy to say, knowing what we know now, that I regret that contract [with Wallis] because it's embarrassing. I was consulted in the procurement process but I didn't hire him. I knew nothing to his detriment."

Sir Paul quit on Sunday after it was revealed that he enjoyed a free five-week stay at Champney's health spa worth £12,000. Mr Wallis was the PR for the spa, but Sir Paul said today that he had not known of the link. He had been in pain and in a wheelchair at the time following an operation to remove a pre-cancerous tumour from his leg.

Sir Paul said he had told Mr Fedorcio to take on "additional support" because his deputy was off sick, but did not put forward Mr Wallis's name. "When Neil Wallis's name came up I would have no concerns about that," he added.

A Downing Street official told Scotland Yard to keep the Prime Minister in the dark about Mr Wallis, Sir Paul said. The disclosure caused surprise because Mr Cameron has since made clear he should have been told earlier that Mr Wallis had been paid £24,000 by the Met for PR advice.

Responding to suggestions that he did not trust the Prime Minister, Sir Paul said he had tried to avoid "compromising" him by revealing operational details about an imminent arrest.

He went on: "I think there is something very relevant here: My understanding is that it was exactly the advice of a senior official in No 10, so we don't compromise the Prime Minister.

"A senior official in No 10 guided us that actually we should not compromise the Prime Minister. And it seems to me to be entirely sensible."

Committee chairman Keith Vaz mocked the appointments of Mr Wallis and former Downing Street spin doctor Andy Coulson, saying they looked like "fashion accessories" and sounded incredulous that Sir Paul never wondered if Mr Wallis had been involved in phone hacking.

"You are a police officer- surely you would have had suspicions?" he said. Committee member Nicola Blackwood suggested Met officers were "blinded by friendship" with Mr Wallis.

The former Met boss also said he regretted the failures of the original investigation and appeared to blame Mr Yates for his decision not to re-open the probe.

Asked about visits to The Guardian in December 2009 to tell them that their stories about phone hacking were "exaggerated and inaccurate", Sir Paul said: "Mr Yates gave me assurances that there was nothing new coming ... I think I had a right to rely on those assurances."

He appeared before MPs as it emerged that Boris Johnson is attempting to rush through the appointment of a new Met commissioner. The Mayor has instructed key staff to look into ways to "speed up" the appointment of a replacement to "restore public confidence in the Met".

Mr Johnson has asked his chief of staff Sir Edward Lister to explore how quickly he can start conducting interviews. Sources said he hoped he may even have a new commissioner in place by the end of next month.