Sir Paul Stephenson will face uncomfortable questions about his association with the former News of the World executive Neil Wallis (Image: Ian Nicholson, PA)

Criticism of the Metropolitan Police's handling of the News International phone-hacking scandal intensified this weekend, following further revelations about the close relationship between high-ranking Met officers and key figures at the embattled newspaper company.

According to The Observer, the Met's commissioner Sir Paul Stephenson had social drinks with the former News of the World executive Neil Wallis on four or five occasions since 2009.

Wallis, who was the deputy editor of the now-defunct tabloid between 2003 and 2007, was arrested on Thursday in connection with phone hacking.

The paper said that the assistant commissioner John Yates had developed a "close friendship" with Wallis over the course of twelve years, dining with the former News of the World executive several times since 2009.

The Metropolitan Police has already admitted to a business connection between Wallis and Scotland Yard's most senior officers. Shortly after the arrest, it disclosed that Wallis had worked as a part-time consultant for Sir Paul and Yates between October 2009 and September 2010.

During that time, Stephenson and Yates met with senior editorial staff at The Guardian in order to lobby the paper to tone down its phone-hacking coverage. Alan Rusbridger, the editor of the paper, wrote to Scotland Yard on Friday to ask why the officers had failed to disclose that they were being advised by a former News of the World executive.

Sir Paul will appear before the home affairs select committee on Tuesday to answer questions about the police's handling of phone hacking. He is likely to face sharp questions about his personal relations with Wallis and other senior officers, having already been forced to defend himself before an emergency hearing of the Metropolitan Police Authority last Thursday.

Sir Paul's judgement again came under scrutiny on Saturday night following the revelation that he received five weeks' free accommodation at a luxury health resort that was being promoted by Neil Wallis' communications firm. According to The Sunday Telegraph, The Met denied impropriety and said that "the Wallis link is a red herring".

Scotland Yard has received persistent criticism over its handling of phone-hacking allegations. Having recovered thousands of pages of notes from the News of the World's private investigator Glenn Mulcaire during their 2006 investigation, police chose not to examine them for evidence of additional criminal activities beyond the paper's royal editor Clive Goodman.

Detectives from the Met's current investigation into phone hacking, Operation Weeting, have now used those same notes to establish that at least 3,870 individuals were targeted by Mulcaire.

Yates received a hostile reception when he appeared before the committee last Tuesday. The committee's chairman Keith Vaz described his evidence as "unconvincing", while another MP derided the assistant commissioner by opining that "you just don't sound like the dogged, determined sleuth that we would expect".

Follow me on Twitter @spyreporteditor for live-tweeting of Sir Paul Stephenson's appearance before the committee on Tuesday (9:00pm AEST, 12:00pm BST).

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