Boris Johnson is not “fit for office”, Sir Keir Starmer said despite the Labour leader’s promise of political unity in the face of the Russian invasion of Ukraine.

The Labour leader said his view of the Prime Minister had not changed but his focus was on Ukraine, rather than domestic political issues.

On Sunday, Sir Keir said it was important that the UK and its politicians “show the world that we’re united”.

The comments were interpreted as a sign that Sir Keir was putting his call for the Prime Minister to quit on hold while the war raged in Ukraine.

Speaking to reporters in London on Monday, Sir Keir said: “My position on the Prime Minister and what I think of him hasn’t changed, I don’t think he’s fit to be Prime Minister.

“But at a time when we’re seeing these desperate scenes from Ukraine, my arguments today, my focus today, is on Ukraine.”

He added: “I do not think he’s fit for office. But it’s very important as Leader of the Opposition, as leader of the Labour Party, that I make clear that my total focus at the moment, as you would expect, is on supporting Ukraine.”

On the BBC’s Sunday Morning programme, Sir Keir said Russian President Vladimir Putin wanted to divide the West, and therefore it was very important to demonstrate unity at Westminster.

“I’m very clear as the Leader of the Opposition, leader of the Labour Party, that when it comes to standing up to Russian aggression, and standing in support of Ukraine, it’s very important in the United Kingdom and in our politics that we show the world that we’re united and, therefore, whatever the challenges and frustrations and criticism I have of the Prime Minister, and I’ve got many on this issue, there is unity, and it’s very important that we demonstrate that unity,” he said.