Sir Keir Starmer has vowed he will lead Labour into the 2026 Holyrood election despite criticism from within his party.

The promise came after Greater Manchester Mayor Andy Burnham said there needs to be “a proper plan for the country” and revealed that some Labour MPs have contacted him to discuss the party leadership.

Speaking to BBC Scotland, the prime minister said he would not comment on Burnham’s “personal ambitions”.

He vowed to deliver change across the UK, and denied that his record in government had derailed Scottish Labour leader Anas Sarwar’s chances of becoming first minister.

Sir Keir also said there was still a chance that Scotch whisky could be exempt from US trade tariffs after he lobbied Donald Trump during his state visit.

After victory north of the border in the 2024 general election, Labour is aiming to return to government in Scotland for the first time since 2007 at next year’s Holyrood election.

However, the party has slipped in the polls since Sir Keir entered Downing Street.

The Holyrood vote will coincide with the Welsh Parliament and English local elections.

Asked if he would lead Labour into all of them, Sir Keir told BBC Scotland: “Yes. When I took over as leader of the Labour Party people told me I couldn’t change the Labour Party, I did.

“When we went into the general election people told me I couldn’t win, we did.

“Now I’m leading the change across the United Kingdom, including delivering better change for Scotland and I’ll continue to do so.”

Sir Keir denied that his unpopularity had ruined Sarwar’s chances of becoming first minister.

“Anas is an excellent candidate who will be incredibly good for Scotland with an absolute focus on delivery,” the prime minister said.

He insisted the pair had worked well together and that they would focus on ousting the SNP from office.

Sarwar, when asked about the prospect of a Labour leadership challenge, told reporters: “I think we should ignore the internal political tittle tattle and get on with delivering for the country.”

The Scottish Labour leader was repeatedly asked if he had full confidence in the prime minister.

He acknowledged that Sir Keir had a “difficult job” and said his biggest criticism of the UK government was that it had achieved “huge successes” but that “very few people had been told about them or know about them”.

Sir Keir denied that he was ruining Sarwar’s chances of becoming first minister and insisted that they “work very closely together”.

He insisted he was delivering for Scotland, citing a £10bn deal for Clyde-built warships to be produced for the Norwegian navy.

Speculation about a Labour leadership bid mounted after Burnham told the Daily Telegraph that Labour MPs had urged him to challenge Sir Keir for the party leadership.

While the Greater Manchester mayor, who is not an MP, said he was not “plotting to get back” to Westminster, he did not rule out a leadership bid.

He later told BBC Radio Manchester: “It’s not up to me, it’s not my decision,” adding that it was a matter for the parliamentary party.

Burnham said that any contest should not focus on personalities and should instead be about a “proper plan for the country, and a proper plan for beating Reform”.

The mayor has proposed raising taxes for higher earners and increasing borrowing to build council houses as he called for the government to “get beyond this thing of being in hock to the bond markets”.

Sir Keir told BBC Scotland: “I’m not going to get drawn into commenting on the personal ambition of the mayor of Manchester.”

He said that fiscal rules were in place to “protect working people” and that economic stability was a “foundational stone” of his government.

“We saw three years ago this week what happened when Liz Truss abandoned fiscal rules,” the prime minister said.

He added: “I’m not going to let that happen under a Labour government.”

Sir Keir also confirmed that he had lobbied the US president for a tariff exemption on whisky during his state visit to the UK last last week.

The Scottish and UK governments are seeking a reduction or removal of the 10% tariff, which the whisky industry says costs businesses £4m per week.

However, Trump flew back to the US without agreeing a deal.

“I absolutely understand how important it is for Scotland,” the prime minister said.

First Minister John Swinney has also discussed the issue with the US president, including during a recent meeting in the Oval Office.

Speaking to reporters on Thursday, he said he had laid the “groundwork” for a deal and that it was for the UK “to get it over the line”.

Asked about speculation over a Labour leadership challenge, he claimed Sir Keir had “spectacularly misused his opportunity of a landslide win”.

Swinney said: “I’ll allow the Labour Party to fall apart as I lead the SNP to the success that we want to deliver for Scotland.”

The answer you would expect from a Scottish Labour leader when asked if they have full confidence in their UK leader is “yes”.

But that’s not how Anas Sarwar handled that question today.

His response to the BBC’s Lynsey Bews did not include a full throated endorsement of Sir Keir Starmer’s leadership.

Instead, he sounded a little more apologetic. He acknowledged that the prime minister has a “difficult job” and suggested that the UK government needed to do much better at communicating its successes.

That came as a surprise, although it is nowhere close to calling for “wholesale change” as the mayor of Greater Manchester Andy Burnham has done.

Sarwar has dismissed talk of new leadership for the UK party as “tittle tattle” but he will be concerned by the trend in opinion polls that suggest his party is heavily trailing the SNP in voting intentions for next year’s Holyrood elections.

He will also know that the prime minister’s personal poll ratings are extremely low and unlikely to offer Scottish Labour an election bounce.

The prime minister’s hope is that by delivering defence orders for Scottish firms and international trade terms that help Scottish workers, he can still boost the Labour brand.