British Prime Minister Boris Johnson cannot answer specific questions over lockdown parties in Downing Street because he does not want to prejudice a police investigation into 12 gatherings, his deputy said on Tuesday.

British police are reviewing more than 500 pieces of paper and over 300 photographs as part of an investigation into whether the Downing Street gatherings broke Covid-19 lockdown laws.

“If he does start answering specific questions that have been referred to the police, he will be accused, in fact fairly and rightly, of prejudicing or preventing or interfering in that investigation,” Deputy Prime Minister Dominic Raab told Sky News.

After initially saying that no rules were broken, Johnson has repeatedly declined to answer specifics about his own attendance at some of the gatherings.

He later admitted being at one gathering but said he thought it was a work event. On Monday, he repeatedly declined to say if he had been at a gathering at his own apartment above the Downing Street office, citing the police investigation into the incident.

Opposition parties said a police inquiry should not preclude Johnson from answering specifics, especially in parliament — the supreme crucible of British democracy.

“What happened was the Metropolitan Police asked that the full report not be published at the moment, but the idea that that prevents the prime minister from saying whether he was at a party on a particular day is absolute nonsense,” Opposition Labour Party leader Keir Starmer told BBC TV.