The Tory party is starting to fall apart before our eyes – no wonder Starmer’s starting to believe in himself

Lee Anderson, a recent deputy chair of the Conservative Party, took his seat on the back row of the opposition benches, next to George Galloway. That is why the expression “crossing the floor” has its power: it is a visual clue to the balance of advantage in the House of Commons.

The balance tilted against Rishi Sunak a bit further today. It was never going to be easy to explain why the Tories should keep the £10m donated by Frank Hester, and the prime minister did the best he could. That involved saying that what Hester said – or “allegedly” said, as Sunak carefully phrased it – was “racist and wrong” but that he had apologised and his “remorse should be accepted”.

There was no chance of Hester’s rather unconvincing remorse being accepted in the unforgiving trading floor of the Commons. Keir Starmer threw it back in Sunak’s face, but before he did he paid tribute to one of Sunak’s predecessors, Theresa May, sitting just behind him. Last week she announced she would be standing down at the election, which gave Starmer the chance for bipartisan graciousness. As Sunak had failed to thank her for her service, Starmer’s chivalry subtly divided the Tories, and implied that her sense of “duty” might have prompted her to hand back Hester’s money.

Another measure of the changing terms of trade in the chamber of the Commons is the noise. The Conservatives understand this, and Marcus Jones, the deputy chief whip, orchestrates the cheering and the barracking each week. But the real din cannot be generated artificially.

Starmer has often used a form of words similar to Tony Blair’s great humiliation of John Major in 1995 – “There’s one very big difference: I lead my party; he follows his.” Today, he did it again to Sunak: “The difference is: he’s scared of his party; I’ve changed my party.” This time, though, there was an unfakeable roar from the Labour benches. They know that it is true – or at least, that it is true enough to win an election for them. They can feel the warm tide of power flowing in their direction.

They took their cue from Starmer’s body language, which is transformed from the days of his early clashes with Sunak. The Labour leader is open and confident. Where Sunak’s counterattacks used to oppress Starmer’s shoulders, he now brushes them aside.

The prime minister had come armed with examples of how Labour’s sums don’t add up, but the Budget last week delivered to the opposition a chance to return fire. Labour has seized on Sunak’s ambition to abolish national insurance contributions altogether in the long term as a £46bn-a-year hole in the public finances.

Not only that, but Starmer went for the disreputable scare tactic of linking it to the funding of state pensions and the NHS. Because many voters believe that national insurance pays for those sacred cows, Starmer accused Sunak of wanting to slay them. It was enough to distract from the prime minister’s attack on Labour’s unfunded spending plans.

The rest of Prime Minister’s Questions went no better for Sunak. Stephen Flynn for the Scottish National Party repeated Starmer’s condemnation of the Hester donations, accusing Sunak of putting “money before morals” – a line that the Labour leader must have wished he had used.

Further evidence of the disintegration of the Tory party was provided by Andrea Jenkyns and Mark Francois. Jenkyns demanded that Britain leave the European Convention of Human Rights – or “at least” put a referendum on it in the Tory manifesto. Francois compared Sunak to Neville Chamberlain and demanded more defence spending. They are fringe characters, but on a day when Sunak was so much on the defensive, they were not helping.

Sunak got through the session, having held the line, in spite of the efforts of Black female Labour MPs, that he shouldn’t return the money to Hester, who had said that Diane Abbott made him “want to hate all black women”.

It was possibly the most uncomfortable half-hour of his 17 months as prime minister. Yet within minutes of his escaping the chamber, the Scottish Conservative Party issued a new declaration of independence. The UK party, it said, should “carefully review” Hester’s donations.

After the Scottish party opposed the government’s extension of the windfall tax on oil and gas in the Budget last week, nothing could more dramatically illustrate a party falling apart. Andrew Bowie, an energy minister and Scottish Tory MP, disowned the policy, as did Douglas Ross, the leader of the Scottish Tories.

The Tory party is falling apart before our eyes. No wonder Starmer is starting to believe in himself.