THE inquiry into partygate will interview Dominic Cummings after the former chief adviser to Boris Johnson said he was willing to swear "under oath" that the Prime Minister misled Parliament.

The PM's former top aide left Downing Street in late 2020 and has become one of the biggest critics of the Tory government since his explosive departure.

Cummings was urged to become a "key witness" to the inquiry being led by senior civil servant Sue Gray (below) into Covid-rule-breaking parties held at the heart of the UK Government.

In an update to his blog on Monday, Cummings suggested that he and "other eyewitnesses" would be willing to swear "under oath" that Johnson "lied to Parliament" about his knowledge of parties happening in Downing Street while the UK was under strict measures to stop the spread of Covid-19.

Misleading Parliament would usually result in a member of the Government, especially the Prime Minister, resigning.

The National: Sue Gray is the senior civil servant leading an inquiry into partygateSue Gray is the senior civil servant leading an inquiry into partygate

Johnson has maintained he believed a party held in Downing Street on May 20, 2020 was a "work event" and that nobody told him it was against the rules.

Cummings refuted that assertion in his blog, claiming that he and others told the PM that the invite sent by Johnson's personal private secretary Martin Reynolds was for an event that clearly broke the rules set by Johnson's government.

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He suggested that the Prime Minister "waved aside" criticisms of Reynolds's invite and allowed it to go ahead with up to 40 people understood to have attended the "drinks party" which were strictly prohibited at the time.

Now it is understood that Gray believes for her inquiry to be credible, all witnesses will need to be spoken to but it is not yet clear whether she has been in contact with Cummings.

A source told the Daily Mirror: "Sue wants the inquiry to be as robust as possible. Cummings is going to be interviewed by the time the inquiry concludes.

"It would be extraordinary if we went through the whole thing and no attempt was made to interview him."