Britain’s MPs are being urged by one of the world’s leading civil-rights lawyers to resist pressure to extend the 28-day time limit for holding terror suspects.

Sir Sydney Kentridge, QC, who once defended Nelson Mandela and the family of Steve Biko during South Africa’s apartheid era, told the Bar Conference in London on Saturday that MPs should be sceptical about moves to go beyond the current 28-day maximum.

There was no discernible evidence to support an extension, he said in a keynote address to more than 500 barristers.

Sir Sydney, who has worked at the South African Bar and the English Bar, said: “While the police here would like 90 days, Prime Minister Gordon Brown said last week that he intended to propose 56 days.

From fat cats to human rights: how the Bar is changing

Bar Conference 2007: Public service is the ethos of the Bar, barristers reveal

• Bar Conference 2007: Programme

What do young barristers think?

Bar Conference 2007: We asked four junior advocates about the main challenges facing the Bar

• Future stars of the Bar 2007

“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.

“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 added: “If any extension at all should be granted, one hopes that Parliament should insist on the closest judicial supervision.”

However, Sir Sydney rejected claims that human rights in Britain had come under attack since the 2001 terrorist attacks in New York and Washington DC.

Sir Sydney, who was remembered fondly in Nelson Mandela’s autobiography, entitled Long Walk to Freedom, also said that he regretted that the law lords had said on Wednesday that it might be reasonable for terror suspects to be given curfews for up to 16 hours a day under the Government’s controversial control orders.

“I consider that the drawing of the line at 16 hours is most disappointing,” he told delegates at the conference in West London.

“And so, I learnt from the newspapers, does the Home Secretary but for diametrically opposed reasons,” he added.

After describing his own experiences of working in the apartheid state, and how South Africa’s black population was denied such basic liberties during that era, Sir Sydney said that current commentators were mistaken in describing the situation as a “sustained attack on hard-fought freedoms”.

“While libertarians, among whom I include myself, must have some cause for concern, on the whole our basic liberties have been defended and preserved notwithstanding the need to meet real and unprecedented terrorist threats,” he said.

“Disappointing to some as this conclusion may be, I discern no concerted assault on our liberty either by those who govern us or aspire to govern us.”

Sir Sydney said that he welcomed proposals from Labour and the Conservatives to draw up a Bill of Rights which would build upon the principles of the European Convention on Human Rights.

Explore Law

• Columnists

• Law Panel

• Law Reports

• Student Law

Times Recommends

• The best legal yarns this Christmas
• Legal school 'earned £1m by exploiting bar course'
• Axe may fall on 5,000 more City lawyers