The Archbishop of York has warned that the government's anti-terror measures are in danger of moving Britain "close to a police state".
Dr Sentamu questioned efforts to extend detentions without charge
Dr John Sentamu, who fled Uganda in the 1970s, criticised 90-day detention, and compared it to his home country under Idi Amin's dictatorial regime.
The archbishop said: "If you detain people, you must have good enough reason for detaining them."
The home secretary moved recently to extend custody limits for suspects.
The limit is currently 28 days for those suspected of terrorism, but yet to be charged.
John Reid told fellow ministers he wanted to try to find cross-party consensus on the controversial issue, at the request of police chiefs.
Government attempts to extend the limit to 90 days failed in 2005, opposed by Tories, Lib Dems and some Labour MPs.
In an interview with ITV's Evening News, Britain's second most senior cleric said: "[The home secretary] has not produced the evidence that shows that in 90 days you're capable of getting somebody prosecuted.
"Why does he want these days, so the police do what? Gather more evidence?
"To me that becomes, if you're not very careful, very close to a police state in which they pick you up and then they say later on 'we'll find evidence against you'. That's what happened in Uganda with Idi Amin."
Meanwhile, West Midlands Police are continuing to question nine people arrested in Birmingham over an alleged plot to kidnap and murder a Muslim soldier.
The archbishop also urged people coming to live in the UK to adopt and "cherish" British values.
"If you are in Britain and you're British, you should really cherish the traditions that are here," he said.
"If you don't actually subscribe to the things that make Britain, you're going to be in trouble."