There is still no evidence Keir Starmer broke Covid rules with a beer and a takeaway meal during a campaign visit to Durham last year, a senior shadow minister has said, saying it was “ludicrous” to suggest the Labour leader was avoiding scrutiny over the issue.

Starmer had been scheduled to attend an Institute for Government event on Monday but has pulled out. Wes Streeting, the shadow education secretary, said he did not know why the decision had been made.

“No idea,” he told BBC Radio 4’s Today programme. “And I didn’t ask before I came on because I just thought it was such a trivial issue. I do think the idea that Keir has been somehow ducking scrutiny on this is ludicrous, given he has been in front of the cameras repeatedly over the weekend.”

Labour has not said why Starmer pulled out of the event.

The event in April 2021, in which Starmer was filmed inside a Durham Labour constituency office holding a beer while people behind him carried plates of food, was examined by local police earlier this year, who said at the time no Covid rules were breached.

But after what the force said was the receipt of “significant” new evidence, Durham constabulary announced last week they were looking again at any potential offences.

It remains unclear what this evidence may be, but over the weekend the Mail on Sunday published extracts from a Labour campaign memo from the period, which set out the timetable for Starmer’s visit, including a scheduled time for a meal. Asked if this undermined Labour’s argument that Starmer was working amid the meal, Streeting said the memo was a “standard visit plan” for such campaigns

“I don’t think anything that I saw in the memo in the Mail contradicted anything that Keir Starmer has said,” Streeting said. “It was a perfectly reasonable thing to do. The only thing I can do is to applaud the Mail for their ingenuity in turning a totally uncontroversial memo into something they are dropping as some kind of great revelation. I just don’t think it is.”

He continued: “I really don’t think that what we have seen, what we’re discussing, is in any way comparable with what we saw in No 10, which is why Boris Johnson was fined, and which is why the public were so angry about suitcases full of booze being wheeled in by officials. It’s just not the same thing.

“I do think we have moral authority to criticise the government, because Boris Johnson has been fined and found guilty of wrongdoing, and Boris Johnson has been proven to have lied to the House of Commons. Keir Starmer has never denied he was in Durham, never denied he stopped for dinner. Boris Johnson denied that there were any parties in No 10.”

Streeting said the fact the memo did not set out specific tasks to be done by Starmer after the takeaway did not mean the Labour leader had, by then, stopped work. “It’s no surprise to any of us who have worked on election campaigns that you might pause for food and you go back to work, you work late,” he said.

Starmer was, Streeting added, “someone of integrity, decency and honesty”, and he was “not even entertaining the prospect” of a fine being levied.

Mary Foy, the Labour MP for City of Durham, in whose constituency office the meal was eaten, denied reports on Monday that some staff had been drunk.

“These allegations about my staff are untrue,” she said in a statement. “I have already said that I and my team were working during a very busy period, including facilitating the leader’s visit. I do not believe either I or my office staff broke any rules.”

The universities minister, Michelle Donelan, told Sky News the fact Starmer was being investigated “smacks of sheer hypocrisy given the relentless focus he has placed on Partygate”. Asked if he should resign if fined, she said: “He’s going to have to search his soul after making this a top priority over the last few months at the expense of key issues like the rising cost of living.”