David Lammy has said it is an “absolute travesty” that details were leaked from a top secret national security meeting on the US-Israel attacks on Iran and has called for an investigation.

There were reports last weekend of cabinet splits at a national security council meeting, which is protected by the Official Secrets Act, over allowing the US to use British bases for the strikes against Iran.

Keir Starmer suggested allowing the US to use the bases to carry out defensive strikes against Iranian targets at the meeting last Friday but was met with opposition from Ed Miliband, Rachel Reeves, Yvette Cooper and Shabana Mahmood, according to the Spectator, a report which was then picked up by several media outlets.

Permission to allow the bases to be used against Iran’s missile sites was granted on Sunday after Tehran had launched a wave of retaliatory attacks against countries across the Middle East.

Asked about the unity of the cabinet on Friday, Lammy told BBC Breakfast: “It’s an absolute travesty that there would be any kind of leak from an NSC meeting and the reason I think that is that it must be right that ministers are allowed to make their assessment supported by the chief of defence staff our intelligence agencies and others and we do nothing that would put our people at risk.

“I will not get into any discussions we had at a national security council meeting.”

The justice secretary added: “The cabinet is absolutely united and supportive of a calm, cool head at this time of being clear we will not be involved in the offensive action but we will absolutely defend our allies and people across the region. The cabinet is entirely united behind the prime minister.”

A leak from the national security council is considered a serious breach. In 2019, Theresa May sacked the then defence secretary, Gavin Williamson over a leak.

Lammy repeated his assertion that any leak was a “travesty” on Sky News and went further, calling for an investigation. “I don’t recognise those reports and I have to say I think it is a travesty that any anyone should report from a national security council … because of course it puts British lives at risk and I hope that is properly investigated,” he said.

At a press conference on Thursday, the prime minister would not be drawn into directly addressing the report by the Spectator. In response to a question from reporters about the unity of the cabinet and the UK decision not to allow the US to use UK bases to launch offensive action, Starmer set out a timeline of discussions between the government and the US.

He said: “No request from the US came in the specific terms that we acceded until Saturday afternoon. Therefore on Friday there was no concrete decision to be made.

“A decision had to be made when we had the request, that came in on Saturday during the course of the afternoon – we were already taking measures in relation to our own capability – that came in on Saturday afternoon, late in the afternoon.

“We then, as you would have expected, went through the details with the US over the next day, and ultimately reached a decision on Sunday, which I announced then on Sunday evening, about eight or nine o’clock.”