President Barack Obama faced condemnation today as he announced he was restarting military tribunals at Guantanamo Bay, reviving the system he once labelled "an enormous failure".

The trial process, set up by his predecessor George W. Bush for fighters captured on the battlefields of Afghanistan in late 2001, was attacked by human rights organisations because it barred defendants from many of the rights they would have in a civilian courtroom.

"This is the best way to protect our country, while upholding our deeply held values."

It was the latest decision by Mr Obama to bitterly disappoint his anti-war supporters on the left. Earlier this week, he announced he would fight the release of up to 2,000 photographs of alleged abuse of detainees in Iraq and Afghanistan – after previously saying they would be published.

Mr Obama said there would be several changes to the tribunal system, which would affect a small number of detainees, including restrictions on hearsay evidence, a ban on evidence obtained through alleged torture and greater scope for detainees to choose their own military counsels.

But these relatively minor alterations were in stark contrast to Mr Obama’s outspoken criticism of a "flawed" system during his election campaign.

In February 2008, Mr Obama described the Guantanamo trials as "a flawed military commission system that has failed to convict anyone of a terrorist act since the 9/11 attacks and that has been embroiled in legal challenges".

The military commissions will remain on hold for another four months as Mr Obama adjusts a legal system that is now expected to try fewer than 20 of the 241 detainees at Guantanamo Bay. Some 13 detainees, including five charged with helping to mount the terrorist attacks of September 11, 2001, are already in the tribunal system.

Mr Obama said: "These reforms will begin to restore the commissions as a legitimate forum for prosecution, while bringing them in line with the rule of law.

"In addition, we will work with the Congress on additional reforms that will permit commissions to prosecute terrorists effectively and be an avenue... for administering justice."

Zachary Katznelson, legal director of Reprieve, the British-based legal action charity, said the changes to the system would do little to improve them.

"After years of working with these bizarre commissions, it is clear to us that they simply do not work," he said. "And unfortunately, the changes the Obama administration has proposed do not begin to address their failings.

"As a constitutional lawyer, Obama must know he can put lipstick on this pig – but it will always be a pig."

Meanwhile it was announced that an Algerian detainee, Lakhdar Boumediene, whose case was at the centre of a Supreme Court battle giving detainees the right to challenge their confinement, had been freed from Guantanamo and was en route to France.