The government of London said it had referred Prime Minister Boris Johnson to Britain’s police watchdog for potential investigation over allegations of misconduct involving a US businesswoman while he was mayor of London.

The Greater London Authority (GLA) said on Friday it had referred a “conduct matter” concerning Johnson to the Independent Office for Police Conduct (IOPC), which investigates complaints connected to the police.

The referral follows allegations, first reported by The Sunday Times, that when Johnson was mayor, he failed to declare close personal links to tech entrepreneur Jennifer Arcuri who received thousands of pounds in public business funding and places on official trade trips.

Asked about the referral, Johnson’s spokesman told Reuters: “The Prime Minister as mayor of London did a huge amount of work when selling our capital city around the world, beating the drum for London and the UK.

“Everything was done with propriety and in the normal way,” he added.

Arcuri did not immediately respond to an emailed request for comment.

The matter has been referred to the police watchdog because Johnson was head of the mayor’s Office for Policing and Crime, a role equivalent to a police commissioner, during his 2008-2016 term as mayor.

Under the referral, the authority will try to determine whether there are grounds for a full investigation that could lead to criminal charges of misconduct in public office.

The GLA said in a statement: “The Monitoring Officer of the GLA has today recorded a ‘conduct matter’ against Boris Johnson and referred him to the Independent Office for Police Conduct so it can assess whether or not it is necessary to investigate the former Mayor of London for the criminal offence of misconduct in public office.”

It said the action had been taken in accordance with the Police Reform and Social Responsibility Act 2011.

Johnson has vowed to take Britain out of the EU by October 31. British parties are discussing tabling a vote of no-confidence in Johnson.