Gordon Brown has been warned by a veteran of the South African anti-apartheid movement that he must withdraw plans to extend detention without charge or face a parliamentary battle royal.
Sir Sydney Kentridge, the civil rights lawyer who represented Nelson Mandela and the family of Steve Biko, said there was no evidence to justify holding terror suspects beyond the current 28-day limit.
Labour is expected to introduce a terror Bill in the Queen's Speech tomorrow which would allow 56-day detention in which a suspect could be questioned without charge. The police want a 90-day detention.
Sir Sydney, who has served at the South African Bar and the English Bar, told the Bar Council's annual conference on Saturday: "While the police here would like 90 days, Prime Minister Gordon Brown said last week that he intended to propose 56 days. One hopes that Parliament will consider that proposal, not merely critically, but sceptically. I have not seen any evidence to justify any extension beyond 28 days."
The last time the Government tried to push through powers for 90-day detention, Parliament rejected them. That, said Sir Sydney, was a victory for parliamentary democracy.
"In apartheid South Africa, the police were given powers to detain suspects without trial for 90 days. Then they asked for and were given 180 days, then presumably because all power is delightful and absolute power is absolutely delightful, they asked for and were given the power to detain indefinitely," he said. "If any extension at all should be granted, one hopes that Parliament should insist on the closest judicial supervision."
Geoffrey Vos QC, the chairman of the Bar, also voiced concerns about the balance to be struck between national security and human rights. But his criticism was mostly aimed at America. He told the conference: "Muslim countries are not impressed with being told that they should adhere to the democratic principles of human rights and the rule of law by a nation that interns people without trial in Guantanamo.