Covid-19: UK police investigating Downing Street lockdown parties

British police will investigate alleged lockdown breaches at Prime Minister Boris Johnson's Downing Street residence after receiving evidence from an internal government probe into a series of gatherings.

Johnson is fighting for his political survival after new allegations that he broke the Covid-19 lockdown rules he imposed by attending a surprise birthday party in Downing Street when social gatherings indoors were banned.

That added to a long list of alleged lockdown breaches in Downing Street, including one 'bring your own booze' party, which Johnson has said he attended thinking it was a work event.

Police will now investigate, London's Metropolitan Police Commissioner Cressida Dick said on Tuesday.

The police investigation could force a delay to the internal inquiry commissioned by Johnson and carried out by senior official Sue Gray, who is expected to report her findings later this week in what was seen as a key moment for Johnson's future as prime minister.