The Leveson Inquiry into press standards turns today to the relationship between journalists and the police.
Former deputy prime minister Lord Prescott and ex-Scotland Yard deputy assistant commissioner Brian Paddick are expected to voice concerns that some officers have become too close to newspaper reporters and executives.
Robert Jay QC, counsel to the inquiry, will begin today's hearing with an opening statement setting out the broad picture of criticism about relations between police and the press.
Earlier this month Lord Prescott and Mr Paddick settled a claim against the Metropolitan Police for failing to warn phone hacking victims at the time of its original investigation into the News of the World (NotW) in 2006.
Paddick, who is the Liberal Democrat candidate in this year's London mayoral election, claimed last July that some police officers had received tens of thousands of pounds for providing reporters with tip-offs.
He told the BBC: "I met a journalist who said he was paying sometimes £20,000 to £30,000 to police officers for information.
"All of this is done in a very clandestine way. You know the stories about a drive-through fast food restaurant near the News International headquarters, that's where police officers used to go to collect envelopes. It was all done very discreetly. I personally never came across it during my career."
Deputy Assistant Commissioner Sue Akers, who is leading Scotland Yard's new inquiries into phone hacking, email hacking and corrupt payments to public officials, will give evidence to the inquiry for the second time today.
Later this week Lord Justice Leveson will hear from ex-Met commissioner Sir Paul Stephenson and his former assistant commissioner John Yates. Both men resigned over the phone hacking scandal.
Scotland Yard's original phone hacking inquiry resulted in the jailing of NotW royal editor Clive Goodman and private investigator Glenn Mulcaire in January 2007 after they admitted intercepting voicemail messages left on royal aides' phones.
However the Met was heavily criticised for limiting the scope of the investigation despite evidence from Mulcaire's notebooks that there could be thousands of hacking victims.
Mr Yates came under fire when he decided not to reopen the phone hacking inquiry after the Guardian published a story in 2009 revealing the illegal practice was far more widespread than previously believed.
Prime Minister David Cameron set up the Leveson Inquiry last July in response to revelations that the NotW hacked murdered schoolgirl Milly Dowler's phone after she disappeared in 2002.
The first part of the inquiry, sitting at the Royal Courts of Justice in London, is looking at the culture, practices and ethics of the press in general and is due to produce a report by September.
The second part, examining the extent of unlawful activities by journalists, will not begin until detectives have completed their investigation into alleged phone hacking and corrupt payments to police, and any prosecutions have been concluded.