The east London politician, a former human rights lawyer, was first elected to City Hall in 2016.
His City and East constituency includes Newham, Tower Hamlets, Barking and Dagenham and the City of London.
In a statement issued through his lawyer in January, Mr Desai confirmed he had been the subject of a recent police investigation, which had ultimately cleared him of any wrongdoing.
However, he did not say what the investigation had been about.
He was administratively suspended from the Labour Party during the investigation – but this paper understands he will be formally readmitted in the coming week.
Neither Mr Desai nor his solicitor responded to our requests for comment about the planned reinstatement.
The statement issued for Mr Desai by Ali Parker, of Saunders Law, in January, said: “Between late December 2024 and today, I was the subject of a police investigation. I have not made any public comment on this until now.
“I cooperated fully with the police investigation. I answered all of the police questions in interview, maintaining my innocence without any legal advice.
“I have today been informed that police are taking no further action in my case. I have always maintained my faith in our system of justice and in the Metropolitan Police.
“I have however been saddened that certain media outlets, political bloggers and users of X (formerly Twitter) have linked my name to this investigation before I was ever charged with any offence.
“Allegations like this spread like wildfire across the internet. In my case, there were very good reasons for pre-charge privacy. It is not right that my name has been tarnished in this way.”
The Met refused to comment on the nature of the probe.
