One of five Britons kidnapped in Iraq more than one year ago has committed suicide, the group holding them claimed in a video to a British newspaper, prompting condemnation from Gordon Brown.

The British prime minister, in Israel after an unannounced visit to Iraq Saturday, condemned the claim to The Sunday Times by the Shiite Islamic Resistance in Iraq and demanded the men's immediate release.

VIDEO: Iraqi video claims hostage suicided

"This abhorrent film will only add to the anguish of families who have suffered a great deal over a year for their loved ones who have been kept in captivity," he said.

Brown said he discussed the kidnapping with his Iraqi counterpart Nuri al-Maliki in Baghdad, adding: "I call on the hostage takers to release these people who have been held in captivity immediately...

"These men have suffered enough."

The video, which was posted on the newspaper's website after being handed to one of its representatives via an intermediary, begins with the photograph of a man, identified only as Jason, alongside the Arabic text of the statement.

An English translation by the weekly said he had slipped into depression and had made more than one attempt to take his life previously.

Jason committed suicide on May 25, 2008 -- four days before the first anniversary of his kidnap -- with the group blaming the "procrastination, and foot-dragging, and lack of seriousness on the part of the British government".

Proof would only be provided if the British government agreed to negotiate, the message added.

The Foreign Office in London said it had no independent verification of the claims.

Foreign Secretary David Miliband said in a statement that the video would cause "deep distress and concern to the families of the five men".

Hostage-taking was a "a disgusting crime which is never justified", he added, emphasising the families' call for their loved ones to be released on humanitarian grounds.

The video -- entitled "Intihar", Arabic for suicide -- repeated the group's call for the release of nine prisoners being held in the southern Iraqi city of Basra in return for the freedom of the hostages.

It then showed video footage of a second man, named by The Sunday Times only as Alan, who said on camera that while he had been treated "very good, to say the least".

But he said he was "not doing well" physically, adding: "Psychologically, I'm doing a lot worse."

He called on the British government to "please hurry" and "get this resolved as soon as possible."

While in Iraq, Brown said he wanted to cut Britain's 4,000-strong force stationed near Basra but refused to set an "artificial timetable" for their withdrawal.

The men -- an IT consultant and his four bodyguards -- were seized by 40 gunmen wearing police uniforms in a daring kidnapping at the Iraqi finance ministry and taken in the direction of the Shiite Sadr City district.

The US commander in Iraq, General David Petraeus, has said the men were being held by a secret cell of the Mahdi Army militia, loyal to the radical cleric Moqtada al-Sadr.

The computer expert has been named as Peter Moore, from the eastern English city of Lincoln, who was working for US management consultancy BearingPoint.

The identity of the other four men has not been revealed, although it is known they were employed by Canadian security firm GardaWorld to guard Moore.

The Shiite Islamic Resistance in Iraq have previously released two videos of their captives.

One of the videos, released in December 2007, showed one of the hostages and demanded that Britain pull out of Iraq within 10 days, but did not say what the consequences would be if it failed to do so.