Scottish Labour leader Anas Sarwar set to become a minister in Burnham's government

When Burnham became prime minister on Monday, Sarwar hailed him for his "bold Labour vision".

Former Greater Manchester mayor Burnham appointed his cabinet on Monday night, but a raft of ministerial appointments are still to come.

BBC Scotland Westminster correspondent Paris Gourtsoyannis said Scottish Labour parliamentarians appeared to have been blindsided by the news.

An MSP called Sarwar's decision "bizarre", while a senior Scottish Labour MP said it was "absolutely mad. I cannot begin to fathom the logic of it."

As a Scottish Labour peer, Sarwar would be entitled to attend meetings of the Scottish PLP at Westminster - a group which earlier this year collectively refused to back their leader's call for Keir Starmer to resign as prime minister.

The SNP's deputy leader Keith Brown said: "This is a terrible look for Andy Burnham who waxed lyrical about a new politics and devolving power - he's just pulled the most undemocratic trick in the Westminster book.

"Anas Sarwar led Scottish Labour to their worst ever election defeat, but as is always the case with the Labour Party, there's always a cushty number in the House of Lords.

"What a signal to send after their democratic defeat - this is the Labour Party literally lording it over the people of Scotland."

Reform UK's Scotland deputy leader Thomas Kerr said: "Only weeks ago, Anas Sarwar stood before the people of Glasgow asking for their trust and insisting that his future was here in Scotland. Today, those same voters will rightly feel betrayed.

"Throughout the election campaign, he dismissed suggestions that he had ambitions elsewhere and claimed his focus was on serving Scotland.

"Now, at the first opportunity, he has walked away from the very people who placed their faith in him."

Jim Murphy, who was Scottish Labour leader from 2014 to 2015, told BBC News: "If it's confirmed I think it's good news for him [Sarwar] personally but it probably, on balance, strengthens the government.

"It will open up a vacancy, of course, for leader of the Scottish Labour Party."

He said Andy Burnham had a maximum three years until the next election and had appointed people he felt could deliver quickly.

"He's come to a judgement that Anas, as part of a wider team, can do that," he said.

"That will be difficult for him [Sarwar]. He will have to get up to speed very quickly but congratulations to him."

Murphy added that there was turbulence whenever there was a leader change within a party.

"I don't enjoy it," he said.

"A good group of really talented people were removed from government yesterday but there are always more talented people than jobs available, so Andy will have to work pretty hard delivering what he promised - which is uniting the Labour tribe to enable them to take on Reform and others."