Police are too often providing unattributable, off-the-record briefings to the media, according to a cross-party committee of MPs.
The Home Affairs Committee said suspects who have been arrested but not charged should not have their names released to the press.
The committee said there were too many leaks from police forces and called for detailed rules on briefings by officers and civil servants during counter-terrorism operations.
Its report, Police and the Media, said there were only a “limited set of circumstances” when it was in the public interest for information about ongoing investigations to be released “off the record”.
But they said forces should give out more attributable information to journalists about individual crimes.
They criticised the decision by West Midlands Police to refer the Channel 4 Dispatches programme Undercover Mosque to regulator Ofcom as “regrettable”.
“Regardless of the rights and wrongs of individual cases, it is not the role of the police to seek to enforce responsible journalism and attempts to do so could be seen as an attack on freedom of expression – all the more so in this case, since the programme dealt responsibly and accurately with extremism and racist comments being made by clerics in places of worship,” the cross party group of MPs said.
Committee chairman and Labour MP Keith Vaz said: “While it may not always be illegal for police to leak to the media it is certainly wrong and can be very damaging to an investigation or to an innocent individual – remember we are talking often about people who have not been charged with any crime or wrongdoing.
“Almost as important, it damages the reputation and integrity of the police themselves.
“The police above all must maintain the highest standards of probity and integrity and we welcome moves to enforce discipline on briefings and develop standard procedures for providing information to the media.”
Liberal Democrat home affairs spokesman Chris Huhne said: “Public announcements are better than private whispers.
“This is a timely message that the police should open up and that the media should grow up.”