Labour leader Sir Keir Starmer has said a photograph of him drinking with a number of party staff in a constituency office last year was “no breach of the rules” and there was “no comparison” with the Prime Minister.

Appearing on the BBC’s Sunday Morning programme, Sir Keir was asked about the picture published in the Daily Mail, which first emerged in spring last year.

Read more: Keir Starmer branded 'hypocrite' over 'lockdown drinking' pictures

The image, which was taken several days before the Hartlepool by-election, was captured through the window of a building in Durham and shows Sir Keir drinking a bottle of beer and standing close to two people while another pair can be seen in the background.

The country was at that time in step two of the road map out of the third lockdown, and indoor mixing between different households was not allowed except for work.

Sir Keir said: “I was in a constituency office just days before the election. We were very busy. We were working in the office.

“We stopped for something to eat and then we carried on working. No party, no breach of the rules and absolutely no comparison with the Prime Minister.”

He added: “It was perfectly lawful to meet for work, which is what we were doing. The party that was put to the Prime Minister on Wednesday happened because an invitation was sent to 100 people saying ‘let’s have some socially distant drinks in the garden and bring your own booze’. There is simply no comparison.”

During the interview, Sir Keir reiterated that Boris Johnson must resign “in the national interest” as he has “lost all authority” in the country.

When asked about Plan B measures, the Labour leader insisted it is important they are lifted because the “medical science says they should be lifted” and not because the Prime Minister is “in a real mess”.

Sir Keir said: “I hope those restrictions can be lifted as soon as possible, but I want them to be lifted because the medical science says they should be lifted, not simply because the Prime Minister is in a real mess and he’s desperately trying to get out of it.

“So, if it’s the right thing to lift those restrictions, we will vote to lift those restrictions. But we’ll be led by the science as we always have been, not by the politics of propping up a broken Prime Minister.”

Shadow health secretary Wes Streeting echoed Sir Keir as he said he could not be confident that the Government was not looking to lift Plan B measures in a bid to shore up Mr Johnson’s leadership.

Told on Sky News’s Trevor Phillips On Sunday programme that Mr Johnson remaining in Government appeared positive for Labour’s approval ratings, Mr Streeting said: “I’ll make no bones about it – Boris Johnson carrying on is great for the Labour Party.

“If I’m thinking purely through the prism of party politics, then my message is: ‘Keep him on, knock yourselves out, you’ll be literally knocked out at the next election’.

“But we are still in the middle of a national crisis here and the Prime Minister’s actions and judgments matter.

“It comes back to the point I made about Plan B measures – if the Prime Minister or the Health Secretary from the Conservative Party is coming forward saying, ‘We’re going to remove Plan B measures’, I want to be absolutely confident they are making that decision in the national interest and not in the party interest, for party management reasons.

“I don’t have total confidence about that.”