DUSK started falling on Sir Keir Starmer’s premiership today as his government was engulfed by an extraordinary outburst of right-on-right political brawling.

The Prime Minister was forced to declare “full confidence” in Health Secretary Wes Streeting in the Commons after Downing Street aides launched a briefing war against the leading Blairite.

Mr Streeting denied that he was plotting to overthrow Sir Keir, following allegations by No 10 that he was plotting to force out the beleaguered and blundering PM.

He instead publicly blamed a “toxic” culture in Downing Street and called for those involved in the briefings, aimed at pre-empting threats to the Prime Minister’s position, to be sacked.

Sir Keir’s top aide, Downing Street chief of staff Morgan McSweeney, was being widely blamed for the fiasco, likely triggered by fears that an unpopular Budget later this month could prompt moves against the premier.

But the briefings only served to bring to the surface hitherto subterranean moves by Labour MPs fearing for their own future in the face of uniformly dismal opinion polling and a crisis of confidence in Mr McSweeney’s own strategy.

The turmoil allowed Tory leader Kemi Badenoch to seize the high ground in the Commons, telling Sir Keir he had “lost control of his government, the confidence of his party and the trust of the British people.”

Sir Keir seemed less than fulsome about Mr McSweeney, but his spokeswoman later stressed he had “full confidence” in the divisive chief of staff, while also condemning all briefings against Cabinet ministers.

But Downing Street seems in no hurry to get to the bottom of the anonymous attacks on a key Cabinet member. And Sir Keir will resist any suggestion that he dismiss Mr McSweeney, without whom he would struggle to function.

Labour MPs, most of whom have only small majorities and would face electoral obliteration on present polling, sat glum-faced at Prime Minister’s Questions (PMQs).

Sir Keir’s claim that he had a “united team” was drowned out by a barrage of jeers, remarkable in an assembly two-thirds Labour.

One centrist Labour MP told the Star that “the mood is terribly gloomy” and that Downing Street had “shot itself in the foot” with the attacks on Mr Streeting. That the anonymous aides described Labour MPs as “feral” did not assist either.

The parliamentary party is now bracing for a breach of the manifesto commitment, little more than a year old, not to raise income tax in Chancellor Rachel Reeves’s Budget.

They believe that will go down disastrously with their constituents, no matter what sweeteners Ms Reeves might offer.

Left MPs dismissed the rows as a diversion from the real issues facing the country.  

Socialist Campaign Group Secretary Richard Burgon said: “Let’s cut through the briefings and counter-briefings — what’s playing out is typical Westminster soap-opera stuff, not a disagreement over policy, principle or vision.

“What’s really needed to prevent a Reform government is a radical change of direction, with real Labour values.”

Another leading left MP agreed that it was “all froth” and that “there is no political substance to it.”

Downing Street sources were insisting that the Premier would resist any move to replace him, which could be triggered by 80 MPs pushing for a contest. In truth, they could say nothing else at this stage.

However, the best reasons they could muster for the status quo were that Sir Keir’s departure would upset the international money markets and US President Donald Trump, not arguments likely to sway all that many Labour MPs.

Many had assumed that any moves against Sir Keir would wait until after anticipated disasters in the May local and devolved authority elections next year.

Since the astonishing Labour wipeout in the Caerphilly election for the Welsh Senedd, however, some MPs have believed that there is little to be gained by waiting to hit the iceberg before changing course.

However, no-one wants to be seen to publicly initiate the regicide. There is the usual talk of a “stalking horse” being promoted to break the ice before serious candidates pile in.

Mr Streeting has been carefully trying to broaden his appeal out from the Blairite hardcore recently, and his prime ministerial ambitions are undoubted.

As well as Mr Streeting, names bandied about include Home Secretary Shabana Mahmood, Education Secretary Bridget Phillipson and for the left in the Cabinet, Energy Secretary and former leader Ed Miliband.

Former deputy premier Angela Rayner is another possibility, but an early contest may be too soon for her, while Manchester Mayor Andy Burnham remains out of Parliament and thus unavailable.

Some MPs believe the socialist left should also field a candidate, although they acknowledge securing 80 nominations would be almost impossible.