Chancellor Gordon Brown's Treasury operates with "Stalinist ruthlessness", treating colleagues with contempt, the ex-head of the civil service has said.
Mr Brown is expected to be the next Labour leader
Lord Turnbull, who was also Mr Brown's permanent secretary for four years, said the chancellor would not allow serious discussion about priorities.
Mr Brown had a "very cynical view of mankind and his colleagues", he added.
But minister Harriet Harman backed Mr Brown, saying: "Not all civil servants admire strong political leadership."
"But if you want to change things for the better you need strong political leadership."
She added, on BBC Radio 4's Today programme: "He is demanding of his colleagues, but he is demanding of himself because he wants to change things for the better."
Lord Turnbull's comments, unprecedentedly outspoken for such a senior civil servant, came in an interview with the Financial Times the day before what is expected to be Mr Brown's final Budget before he succeeds Tony Blair as prime minister.
The Treasury has refused to comment on the Financial Times interview.
Lord Turnbull also declined to discuss his comments on the Today programme because he thought he had done "enough damage already".
BBC political editor Nick Robinson said he had been told that Lord Turnbull thought he was talking off the record.
In the FT interview, Lord Turnbull said of Mr Brown's relationship with his colleagues: "He cannot allow them any serious discussion about priorities. His view is that it is just not worth it and 'they will get what I decide'.
"And that is a very insulting process."
He said this strategy had enhanced Treasury control but had come "at the expense of any government cohesion and any assessment of strategy".
Lord Turnbull added: "You can choose whether you are impressed or depressed by that, but you cannot help admire the sheer Stalinist ruthlessness of it all."
He said "the chancellor has a Macavity quality. He is not there when there is dirty work to be done".
However, he praised Mr Brown for his move to allow the Bank of England to be independent.
He added that what surprised him about the Treasury was "the more or less complete contempt with which other colleagues are held".
Departments were told only at the last minute what their Budget settlement would be, he added, claiming the man who expected to be the next prime minister used denial of information as an "instrument of power".
Labour MP John McFall, chairman of the Commons Treasury select committee, told Today there was a "need for more coherence in government".
He added: "I actually see Gordon Brown as a 24-hour-a-day politician."
Mr McFall also said: "I actually think Gordon has been ruthless in terms of getting delivery... [He is] a 24-hour-a-day politician who is very, very committed to people."
Former Conservative defence secretary Michael Portillo said Mr Brown's "personality and qualities have led him (Lord Turnbull) to be outraged".
He added: "He's (Lord Turnbull) a bit of a stickler for convention and doesn't like things done in a rude way and perhaps he thinks Gordon Brown does things in these ways."