London mayor Boris Johnson acted in an "extraordinary and unwise" way by contacting Conservative MP Damian Green while he was the subject of a police investigation, an independent report found.
The report, by solicitor Jonathan Goolden, also warned that Mr Johnson could "inhibit free and frank discussion of operational matters" with senior police officers if he continued to publicise his reaction to their briefings, as he did in the Green case.
But Mr Goolden cleared the mayor of breaching the codes of conduct of either the Greater London Authority (GLA) or the Metropolitan Police Authority (MPA), which he chairs.
His report recommended that the GLA, MPA and Metropolitan Police agree a new joint protocol for the handling of information from senior police officers by the mayor and MPA members in the event of a critical incident.
The inquiry was sparked by a complaint from Labour's leader on the GLA and MPA member Len Duvall about Mr Johnson's actions following the arrest of the Tory immigration spokesman - a friend of the mayor's - on November 28 last year in relation to a police investigation into alleged Home Office leaks.
The acting commissioner of the Metropolitan Police Sir Paul Stephenson informed Mr Johnson a few minutes in advance of the plan to arrest Mr Green, and the mayor discussed the reasons for arrest with Sir Paul after it had taken place later that day.
A press release was issued that evening by Mr Johnson's spokesman, indicating that the mayor had voiced concern about the arrest. Mr Johnson then spoke by telephone with Mr Green on December 1 about the police investigation.
The following week, Mr Johnson told a meeting of the London Assembly that he had an "instinct and a hunch" that the police investigation would "probably go very badly" and was unlikely to result in a charge.
The GLA and MPA commissioned Mr Goolden's report after Mr Duvall complained that the mayor had breached their codes of conduct by making public his conversation with Sir Paul, discussing the police investigation with Mr Green and commenting in public on the investigation.
