DOUGLAS Ross has been challenged to “grow a backbone” and resubmit his letter of no confidence in the Prime Minister in light of bombshell photographs of a Downing Street party during lockdown.

The Scottish Tory leader has flip-flopped on whether Boris Johnson is fit for office after reversing his previously critical position on the Prime Minister following the invasion of Ukraine.

But new photographs published on Monday by ITV News show the Prime Minister at a party in Westminster on November 13, 2020 – when the country was in strict lockdown and indoor socialising was banned.

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The pictures show the Prime Minister making a toast and feature a table laden with bottles of wine and empty glasses, as well as biscuits, crisps and a takeaway container.

The SNP said the pictures “proved beyond all doubt” the Prime Minister had lied to parliament after he repeatedly claimed all rules had been followed in No 10 during lockdown.

Kirsten Oswald, the party’s deputy Westminster leader, said Ross must resubmit his letter of no confidence “without further delay”.

She added: “By constantly flip-flopping over Boris Johnson's future, the Scottish Tory leader has blown any remaining credibility - and shown himself to be a weak and unprincipled lame-duck leader.

"The Scottish Tories have run out of excuses. The longer they leave Boris Johnson in office the more damage they will do to public trust in this out of touch UK Government.

"Tory MSPs should speak out like they overwhelmingly did in January.”

Johnson specifically denied a party taking place on the date the photographs were taken when asked about the event, telling the Commons: “I'm sure that whatever happened, the guidance was followed and the rules were followed at all times."

READ MORE: Boris Johnson denies telling Sue Gray to conceal partygate report

Ross had been one of a number of high profile Tories to call on the Prime Minister to resign when it was revealed parties had taken place in Downing Street during lockdown.

He sent a letter of no-confidence to Graham Brady, the chair of the Tory group of backbench MPs called the 1922 Committee, which has the power to instigate a vote of no-confidence.

Following Vladimir Putin’s invasion of Ukraine, the Moray MP retracted his letter and argued it was not the right time for a change of leadership, pointing to Ukrainian President Volodymyr Zelenskyy’s praise for Johnson.

The Scottish Conservatives were approached for comment.