Leishman entered Parliament as one of the few members of Labour's 2024 intake prepared to attack his own government openly. His political standing came less from a party position than from becoming the loudest parliamentary advocate for Grangemouth's industrial workforce.

That approach quickly put him at odds with Keir Starmer. Leishman opposed the government's disability-benefit reforms and joined the Labour rebellion against the Universal Credit and Personal Independence Payment Bill. In July 2025, Labour withdrew the whip for what the party called repeated breaches of discipline. It was restored four months later after a review by the new chief whip.

The sanction did not silence him. In February 2026 he said Starmer's position had become untenable and called for Labour to return to "real Labour values". This placed him firmly against the party leadership months before Starmer's eventual resignation. He subsequently nominated Andy Burnham in the 2026 leadership election.

What he stands for

Leishman's politics is based on redistribution, public ownership and protection for organised labour. He has advocated an annual two per cent tax on assets above £10 million, arguing that it could fund public services and reduce inequality. He has also called for capital gains to be taxed more like employment income.

At Grangemouth, that outlook translated into demands for direct state intervention. When the government moved to take control of British Steel's Scunthorpe operations, Leishman argued that Scotland's refinery deserved the same treatment and should be nationalised if necessary.

His welfare rebellion followed the same principle. He accepted that the system could be reformed, but rejected using lower payments to disabled people as the means of saving money. Unlike several figures on Labour's left, he remained in the party after losing the whip. His position was that Labour had abandoned its own purpose, not that Labour itself should be abandoned.

What he actually delivered

Leishman's clearest result came from the part of the Grangemouth complex that remained open. In December 2025 the government provided more than £120 million, within a wider £150 million agreement with Ineos, to keep the ethylene plant operating and protect 500 jobs. Leishman did not negotiate the package, and ministers and officials deserve the principal credit. There is, however, evidence that his pressure mattered. The responsible minister confirmed that he had spoken with Leishman during the preceding weeks and valued his contribution; Conservative David Mundell also credited him as a persistent advocate for the workforce.

He also contributed to a wider welfare revolt that materially changed government legislation. More than 120 Labour MPs threatened to oppose the original proposals, while Leishman remained among the 47 who voted against the final bill. Under that pressure, ministers removed the provisions tightening eligibility for Personal Independence Payment and proceeded with a much narrower Universal Credit measure. This was a collective backbench victory rather than Leishman's alone, but he accepted a political sanction for maintaining his opposition.

What he failed to deliver

The central promise of Leishman's 2024 campaign was blunt: "Only voting Scottish Labour on 4th July can save the jobs at the Grangemouth refinery."

It did not happen. The refinery stopped processing crude oil on 29 April 2025. Its workforce fell by roughly 400 as it became an import terminal. Labour neither nationalised the operation nor kept it refining.

The government announced £200 million from the National Wealth Fund for new Grangemouth projects, but the money depended on investable proposals and private co-investment. As late as June 2026, the investment taskforce was still identifying interested businesses and assessing possible projects. Announced green ventures carried forecasts of hundreds of jobs over several years, not completed replacement employment for the refinery workers.

Leishman has shown that a first-term backbencher can withstand party punishment, help force changes to legislation and keep an industrial crisis on the government's agenda. He also helped create pressure around the intervention that protected 500 chemical-plant jobs. But his defining election promise was not delivered. His record shows courage and campaigning ability more clearly than control over outcomes.