British police said on Tuesday they had opened an investigation into possible Covid-19 lockdown breaches at Boris Johnson’s Downing Street office and residence, the latest blow to a Prime Minister facing growing calls to resign.

Boris is fighting for his political life after allegations that he and staff partied at the heart of the British government in breach of rules they had themselves imposed to fight the pandemic.

Revelations of revelry including boozy parties in Downing Street, suitcases of supermarket alcohol, a broken children’s swing, a wine fridge and jokes by staff about how to present such parties to reporters, have hammered Boris’s ratings.

ITV reported on Monday that Boris and his now wife Carrie had attended a surprise party of up to 30 people for his birthday at No 10 Downing Street on June 19, 2020, when indoor gatherings were banned.

A spokesman said Boris did not believe he had broken the law over any of the gatherings.

“I welcome the Met’s (London Metropolitan Police) decision to conduct its own investigation because I believe this will help to give the public the clarity it needs and help to draw a line under matters,” Boris told Parliament.