A retired head of Scotland Yard today criticised his former force's failure to investigate fully allegations of widespread phone-hacking at the News of the World.
Lord Stevens told the Leveson Inquiry he hoped he would have been "quite ruthless" about pursuing claims in 2009 that the illegal practice was far more prevalent than previously believed.
Fellow former Metropolitan Police commissioner Lord Condon said he was "very disappointed and concerned" by issues about the behaviour of Scotland Yard officers exposed by the press standards inquiry.
Scotland Yard's original phone-hacking investigation resulted in the jailing of News of the World royal editor Clive Goodman and private investigator Glenn Mulcaire in January 2007 after they admitted intercepting voicemail messages left on royal aides' phones.
But the Met was widely criticised for failing to reopen the probe after the Guardian published a story in July 2009 alleging there were more journalists and many more victims involved in the case.
Lord Stevens, who was head of Scotland Yard from February 2000 to February 2005, told the Leveson Inquiry today: "Like Paul Condon, I have been disappointed with what has taken place.
"I would like to have thought that the issues with the Guardian that were raised, I would have picked up as commissioner.
"If they had been picked up then, I think I would have been quite ruthless about pursuing it."
Lord Stevens terminated a contract to write a column for the News of the World at £7,000 per article in October 2007 over concerns about the phone-hacking convictions and other "unethical behaviour" at the paper, the inquiry heard.
"I would never have written the articles if I had known what I now know," he said.
"By terminating the contract with five articles to write, I was throwing away money, but that didn't worry me."
The inquiry heard that Lord Stevens dined with former News of the World executive editor Neil Wallis both privately and for work.
On two occasions their wives were present as they discussed the former policeman's charity, Convoy 2000.
Lord Stevens said his relationship with Mr Wallis was "totally professional" and would not have affected any decision to investigate the News of the World.
"I am afraid if it comes to enforcing the law, any relationship has to go to one side," he told the hearing.
"If there is evidence to pursue in terms of any criminal activity, whether it be phone-hacking, corruption or otherwise, that has to be pursued."
The former commissioner also had meals with then News of the World editor Rebekah Brooks, who was always trying to persuade him to support her campaign for a "Sarah's Law" giving parents the right to know if a paedophile was living nearby, the inquiry heard.
Lord Stevens also accused former home secretary David Blunkett of briefing the media against him.
He said: "Every now and again I was seeing headlines saying he was going to sack me and things like that, which of course had never been said to my face.
"I found that quite difficult, especially as we were getting superb results."
Asked whether he was saying that Mr Blunkett was briefing the press behind his back, the former commissioner said: "Yes."
The inquiry heard last week that a number of senior Met officers dined at fine restaurants and drank champagne with News of the World journalists after the paper was investigated for phone-hacking.
News of the World crime editor Lucy Panton was told by her newsdesk in 2010 to "call in all those bottles of champagne" to get inside information about a terrorist plot from John Yates, Scotland Yard's then head of counter-terrorism.
Lord Condon, who was Met commissioner from 1993 to 2000, told Lord Justice Leveson today: "Based on what is in the public domain, primarily from what has happened in your inquiry, sir, I have been very disappointed and concerned by some of the issues that have emerged.
"And had I still been involved in the service, I would have been probably very angry."