Sue Gray’s investigation into Partygate could be split in two as a result of the investigation launched by the Metropolitan Police, Downing Street has suggested.

The prime minister’s spokesman said the inquiry’s terms of reference made clear she could not reveal her findings on gatherings subject to a police probe.

It means the full results of Ms Gray’s investigation may not be known for months.

Met Commissioner Cressida Dick confirmed this morning that detectives will investigate “a number” of parties alleged to have taken place in Downing Street during lockdown.

In a briefing for journalists, the prime minister’s official spokesman said that effectively meant Gray report will be in two parts.

He said: “As the terms of reference make clear, they won’t publish anything that relates to the work of the police.

“There are a number of events and allegations that they have looked into that the police said don’t reach their threshold, which they are able to continue looking into. And it is my understanding that they will be able to publish detail about those events rather than ones which the police might be taking forward.

“It’s up to the investigation team when they publish, it’s my understanding they are able to publish the aspects that aren’t a matter for the police.”

Number 10 later denied claims that it was trying to delay the publication of Gray report.

The prime minister’s spokesman said talks were continuing between the police and the inquiry team over how much could be published and when.

He said: “I have seen reports suggesting that we were seeking to prevent the publication and that is not accurate.

“There are discussions still ongoing between the investigations team and the police.

“That still needs to be worked through both in relation to what may or may not be published and the ongoing work of both the police and the investigation.”

Cressida Dick announced the police investigation at the London Assembly.

She said: “What I can tell you this morning is that as a result of the information provided by the Cabinet Office inquiry team and, secondly, my officers’ own assessment, I can confirm that the Met is now investigating a number of events that took place at Downing Street and Whitehall in the last two years in relation to potential breaches of Covid-19 regulations.”

It has also emerged that Boris Johnson decided not to tell his Cabinet colleagues about the Met probe, despite being told about it before their weekly meeting this morning.

The prime minister’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”.