Officials and police should be subject to new rules covering media briefings on anti-terrorism investigations, human rights organisation Liberty has said.
Leaks could disrupt police operations, Liberty says
The group says the lack of protocol on how to brief reporters is "potentially disastrous", damaging police operations and the ability to hold fair trials.
Senior anti-terror police have recently expressed concerns that unauthorised leaks could put lives in danger.
Ministers say civil service rules already forbid such leaks.
Under section six of the Civil Service Code, government workers are not allowed to "disclose official information without authority".
"This duty continues to apply after you leave the Civil Service," the code adds.
Liberty wants new rules to be brought in immediately to cover police officers and civil servants, including government "spin doctors".
The group's spokeswoman, Shami Chakrabarti, said getting accurate information to the public was "vital in the face of the terrorist threat".
"So it's high time that there were clear protocols to avoid the distorted, unaccountable and badly-timed briefings that are so damaging to police operations, fair trials and community confidence."
In a research paper, Liberty highlighted the Forest Gate raids in June 2006 - after which no-one was charged - and the "ricin plot" of 2003, which found no evidence of the poison.
Liberty says media coverage of both operations featured widespread allegations attributed to anonymous sources.
The group called for a commission to be set up to draft new protocols.
"The guidelines should ensure that information comes from appropriate and readily identifiable sources within the police or civil service to allow for proper accountability," the paper said.
"Failure to adhere to the guidelines will be a disciplinary matter."
Peter Clarke, the UK's counter-terrorism chief, said two weeks ago that secret briefings were being used by individuals to "squeeze out some short-term presentational advantage".
The Home Office said at the time it agreed with Mr Clarke, adding it had a policy of never commenting on operational matters.