Boris Johnson failed to tell his Cabinet colleagues that the Metropolitan Police were about to announce a probe into partygate.
The prime minister was told Cressida Dick was going to confirm the investigation shortly before his weekly meeting with senior ministers.
However, he decided not to mention it to any of them, meaning they only found out about it after Cabinet ended.
Johnson’s spokesman said: “It’s important not to pre-empt a police statement on this sort of issue at any point.”
Instead, the spokesman said the prime minister had “alluded” to the ongoing row at the end of Cabinet by “emphasising there was more work to do to deliver for the public and that the government would not be deterred from getting on with the job”.
Meanwhile, No. 10 have also confirmed that Johnson is willing to be interviewed by police leading the probe.
Asked if the prime minister would submit himself to questioning, his spokesman said: “Everyone required will fully co-operate in any way they are asked to.”