Secret media briefings by the Home Office could undermine the police investigation into an alleged kidnap plot, a human rights group says.
Police have been searching address in several part of Birmingham
Liberty has written to Home Secretary John Reid asking for details of all briefings given to journalists about last week's West Midlands terror raids.
Nine people are in custody suspected of planning to murder a Muslim soldier.
The group is also worried officials who talked to the media were asking for more time to hold terror suspects.
Liberty director Shami Chakrabarti said she was "gravely concerned" by reports the Home Office may have "secretly and speculatively briefed journalists as security operations were under way".
"Any such practices risk undermining the work of police and prosecutors and jeopardise both the trust and safety of the public.
"If the same people have offered secret anti-terror briefings whilst proposing the extension of pre-charge detention, this would be party politics at its most dangerous."
Last week, a judge granted detectives until Tuesday to question the men.
Terror suspects can be held for up to 28 days without charge - but only if police can persuade a judge they need more time.
West Midlands Police confirmed on Monday that they had completed searches at 18 properties and said they intended to "review the detention" of the suspects.
The nine men were arrested last Wednesday under the Terrorism Act over what security sources say was a plan to film the murder of a British soldier and post it on the web.
Following the arrests, forensic teams have been combing addresses in the Sparkhill, Alum Rock, Kingstanding and Edgbaston areas of the city.