Sir Keir Starmer has said the police “have got their job to do” but denies the event in the City of Durham broke any rules.
The Labour leader said there was “no party, no breach of the rules” on a visit during which he drank beer in MP Mary Foy’s office.
Durham police initially concluded that no offence had occurred on 30 April last year, but said it had since received “significant new information”.
It added that it had delayed announcing the investigation until after Thursday’s local elections.
