Labour’s only MP in Scotland has resigned from Jeremy Corbyn’s shadow cabinet.
Ian Murray’s resignation could prove pivotal in bringing down the UK Labour leader, who has been accused of running a lacklustre referendum campaign and has failed to win the backing of many of his MPs.
The Edinburgh South MP announced he had written to Mr Corbyn to tender his resignation at midday on Sunday Politics Scotland.
There is no other Labour MP in Scotland that could replace him as shadow Scottish Secretary.
Five of the shadow cabinet have now quit and another has been sacked in another turbulent day for UK politics.
Mr Murray told the BBC: “I just don’t think that Jeremy Corbyn is able to lead us, to be prime minister, and I am not just doing this in public, I raised it at our emergency shadow cabinet on Friday.
“I did say to the shadow cabinet, and to Jeremy directly, that I didn’t think, at this moment in time, that he could be prime minister, and if he thought he could be prime minister, then he’s talking to the wrong people, and needs to change.
“His change seems to have been to sack Hilary Benn. I think that’s the wrong way to go, and I think this is the final straw for many people in the shadow cabinet who served for unity in the party and also in the country, but we do need change now because the Labour Party cannot win a general election in its current state.”
Scottish Labour’s deputy leader Alex Rowley attacked Mr Murray’s decision.
The Fife MSP tweeted: “Disappointing that at a time when we need unity, focus & strength @IanMurrayMP and fellow plotters put self interest before needs of country.”
Faced with mass resignations, a defiant Mr Corbyn has said he would simply replace anyone who left the shadow cabinet.
But the departure of Mr Murray, who is the shadow Scottish Secretary and Edinburgh South MP, would be fraught given there are no other Labour MPs in Scotland to step in as his successor.
Mr Benn, the shadow foreign secretary, was sacked last night after he told Mr Corbyn he had lost confidence in him.
Heidi Alexander, the health secretary, has resigned with Mr Corbyn likely to face motion of no confidence that would lead to a leadership contest.
Also stepping down are Gloria de Piero, Lillian Greenwood and Lucy Powell.
Shadow chancellor John McDonnell has insisted Mr Corbyn is “not going anywhere” as he ruled out himself out of standing as his successor.