With an election due by June and the ruling Labour Party behind the opposition Conservatives in the opinion polls, the issue of Brown’s style of leadership has been top of the media agenda since a Sunday newspaper published bullying allegations.

“I would never instruct anybody to do anything other than support my chancellor,” Brown told ITV television early on Wednesday, reacting swiftly to the comments by Darling, whose title is Chancellor of the Exchequer.

In a Sky News television interview late on Tuesday, Darling said aides to Brown had given negative off-the-record briefings to media about him after he told a newspaper in 2008 that economic conditions in Britain were the worst in 60 years.

“I’d done this interview and the forces of hell were unleashed,” Darling said. “I do not know why the briefers, if you like, did what they did. One day maybe they’ll explain.”  

He made clear he was referring to aides and said nothing to suggest that Brown was personally responsible for the bad press.

The Conservatives jumped on Darling’s comments, saying they had “blown apart” the idea that Brown ran a happy, united team.

Questions about Brown’s working relationships have dominated the political debate since the Observer newspaper published allegations that he had terrified staff by screaming at them and on occasion had physically intimidated them.

Brown, the son of a Scottish clergyman, has often been criticized for his stiff manner, but in recent television appearances he has shown a more sensitive side. The strategy appears to be working, with Labour closing the gap with the Conservatives in the opinion polls.

Some analysts say that far from damaging Brown, the attacks on his character might help endear him to voters by showing him as a flawed human being who got stressed like anyone else.

Darling’s comments cast fresh light on a period of financial turmoil in 2008 often described as a moment when Brown showed his quality, helping avert a global economic meltdown.