Staff on the BBC's flagship news magazine programme have been browbeaten more than most by Mandelson and Tony Blair's press supremo, Alastair Campbell. Indeed, such is this duo's determination to control the news agenda that the nature of Newsnight will soon be drastically altered to deal with their spindoctoring.
Jeremy Paxman - who's taken the summer off to write a book at home in Oxfordshire - will return next month as the main anchor, with Kirsty Wark taking over two nights a week. (Gavin Esler and Huw Edwards, keeping the show going over the summer, will fade into the background, and Peter Snow has retired.) But the format of the programme will be decidedly different. There will be less emphasis on aggressive interviews with government ministers and their shadows and fewer hard-edged current affairs films. Instead, we will be served up politics with a lighter touch and the sort of cultural items which used to feature after Newsnight on The Late Show. In short, less analysis, more attitude.
The pacifying of Paxman will please not only Peter Mandelson but also a man Mandelson worked for early in his career and has remained friendly with - the BBC's director-general John Birt. Just over two years ago, in a lecture at Trinity College Dublin, Birt launched an astonishing attack on "sneering, overbearing interviewers" whose "ritualistic encounters" and "bickering" with ministers could mask the real political issues.
The DG later claimed he was speaking about the media in general and not slagging off his own staff, but his outburst was seen as a coded attack on Paxman and John Humphrys, presenter of Radio 4's Today programme.
The BBC experimented with a new softer Newsnight format during the general election campaign, when Paxman hosted a series of Saturday-night specials featuring not just party politicians but a range of celebrities. Among those who joined him to take an irreverent look at the campaign were Gore Vidal, the American novelist and satirical essayist, Jo Brand, the stand- up comic, and Mick Hucknall, lead-singer of Simply Red. Peter Horrocks, editor of Newsnight, deemed the experiment a success, not least because the programmes - granted an early evening slot - drew an audience of 1.3 million - about four times what Newsnight gets on a bad night.
Horrocks told reporters at the launch of the BBC's election-night coverage - which he also masterminded - not to be surprised if the lessons learned from these softer Saturday-night specials were soon fed into the main evening programme.
In the eve-of-election excitement no one was thinking ahead to the autumn. But it has since become clear that Horrocks was signalling a new direction for Newsnight.
His desire to change the programme has been heightened during the first 100 days of New Labour rule. Horrocks has been heard to ask lately: "How do we deal with a very media-savvy government and an opposition which isn't that effective?" His conclusion is that a new style of political coverage is needed. Paxman is understood to be in favour of the new format; he, too, had grown frustrated by the ritualistic confrontations.
But other senior figures in the BBC News directorate believe the changes at Newsnight are part of a disturbing trend - a general marginalisation of serious current affairs inside an increasingly ratings-obsessed and cost-conscious corporation.
To these internal critics, taking the news out of Newsnight is part of wider trend which has seen the BBC's flagship current affairs documentary strand Panorama moved back on the Monday schedule to 10pm and the weekly political programme On the Record moved forward to an earlier Sunday lunchtime slot where the available audience is significantly reduced. Public Eye has been axed completely.
One senior programme-maker, who wished to remain anonymous, told The Independent: "Newsnight has for some time had trouble getting government ministers on when it wants them. That difficulty started under the Tories. But it would be disgraceful if the programme was changed simply because the government won't play ball.
"No matter what Mandelson and Campbell do, the BBC should not suspend its critical faculties and give this government an easy ride just because it is superficially popular."
The suspicion of many in the current affairs division of the BBC News directorate is that Newsnight is being reformatted to save money. Established current affairs programmes will have to absorb a budget cut of more than 13 per cent in the next four years to fund the BBC's forthcoming 24-hour news channel.
"We simply cannot afford to do the same sort of probing, thoroughly researched current affairs journalism when resources are being diverted into round- the-clock rapid response newsgathering," said another critic of the impending changes. "Newsnight is going to become a more studio-based programme because of budget constraints. Luvvies will be wheeled in to lighten up what could otherwise be a very tedious format."
Whatever the motivation behind them, the changes to the BBC's current affairs output plainly fly in the face of the "mission to explain" philosophy which John Birt sought to bring to the BBC when he took charge of its news and current affairs department a decade ago.
Birt first developed this philosophy while in command of Weekend World for LWT. One of the bright young researchers on that Sunday lunchtime programme was Peter Mandelson, who is now plainly bent on ensuring that no member of the new Labour government ever has to undergo the sort of sustained, rigorous grilling to which ministers were routinely subjected by Brian Walden.
Charles Leadbeater, who also worked for a while on Weekend World, believes that the BBC leadership has now fixed its eyes on bigger targets than the mission to explain. He wrote recently in the New Statesman: "Those who feel most aggrieved are the true Birtist camp followers, who feel they are being betrayed by their great leader. Birt, they say, has simply junked his own creed."
Leadbeater quoted a former "missionary of explanation" who told him: "Birtism has been stood on its head. The idea was that serious journalism should put stories in context and analyse them. That is all being abandoned. Birtism is dead. The Cultural Revolution is over, but Chairman Mao is still in power".