Senior police officers say their calls to be allowed to hold terror suspects for longer without charge would not mean any kind of "internment".
Acpo says the current detention limit is not long enough
"We are not arguing for some kind of Guantanamo nonsense for the UK," said Ken Jones, head of the Association of Chief Police Officers (Acpo).
Mr Jones said the police needed more flexibility over the current limit of 28 days without charge.
Shami Chakrabarti, of campaign group Liberty, attacked the police proposal.
"We elect politicians to determine legislation and we expect chief constables to uphold the rule of law, not campaign for internment," said Ms Chakrabarti, director of Liberty.
'Against the buffers'
The head of the senior police officers' organisation had warned in a newspaper interview that terror investigations were "up against the buffers on the 28-day limit" - and that suspects should be held for "as long as it takes".
But facing criticism over such an open-ended form of detention, Mr Jones sought to clarify what flexibility the police needed in such cases. "We do not want internment. That would be crazy."
"It needs to be as long as is proportionate and necessary, subjected to sufficient judicial checks and balances," Mr Jones told the BBC. "But I can tell you now, Acpo is not calling for indeterminate detention."
The Metropolitan Police distanced themselves from any calls for indefinite detention. "Any such proposal would not have the support of the Metropolitan Police service."
The government's independent reviewer of terrorism legislation, Lord Carlile said the issue was not simply about the number of days someone should be detained.
"My view is that people should not be detained a day longer than necessary or a day shorter than necessary in the interests of justice," he said.
"The cases should be considered by senior judges on an evidence basis. It would strengthen the rights of those detained with a higher level of judges and subject to appeal."
And extending the detention period without trial was rejected by the Shadow Home Secretary, David Davis.
"All the evidence shows that when the police tried to claim the need for 90-day detention without charge they were wrong and Parliament's decision on 28 days was right," said Mr Davis.
"Since the 28-day limit was introduced neither the police or security services have produced one shred of evidence to demonstrate the need for extension, either in public or in confidential briefings," said Mr Davis.
Liberal Democrat MP, Evan Harris, also condemned the calls for such an extension.
"The police have not provided evidence from their experience of recent investigations that the current 28-day limit - already one of the longest for a democracy - is not sufficient to collect evidence to bring charges," said Dr Harris.
The government has tried to raise the limit a suspect can be held without charge to 90 days.
But MPs have consistently rejected that proposal - handing former Prime Minister Tony Blair his first defeat in the Commons, in 2005.