The number of reports made to the Metropolitan Police internal whistleblowing service has fallen by 23 per cent since 2017, despite an increase in external reports.

A total of 296 reports were made to the Met’s “Right Line” service in 2020/21 compared to 384 during 2017/18. But reports made by Met officers to the Crimestoppers “Integrity Line” increased by 13 per cent in this same period.

The Metropolitan Police Service was unable to confirm how many reports led to misconduct investigations.

The figure was revealed by Mayor of London Sadiq Khan following a question from Labour London Assembly Member Unmesh Desai at a recent City Hall meeting.

Read more: Met Police receive thousands of complaints in detailed new report

It comes amid accusations of a “canteen culture” within the Met as the force faces increasing scrutiny following several high-profile incidents including the murder of Sarah Everard by a Met officer, as well as recently revealed failings in the investigation of serial killer Stephen Port.

Sadiq Khan has said that “we need to completely transform the culture in the police service and be reassured that it’s been transformed” but suggested that the fall in internal whistleblowing reports could be because there are other channels through which officers can report inappropriate behaviour or misconduct.

But Unmesh Desai, who requested the figures, said that it was “concerning” that internal Met whistleblowing reports had fallen.

Mr Desai said: “The fall in use of the whistleblowing hotlines by Met Police staff is concerning and I am keen to get to the bottom of the factors behind this.

London Assembly Member Unmesh Desai

London Assembly Member Unmesh Desai

“With the Met Police trying to rebuild Londoners’ trust and confidence by reinforcing their standards and integrity, it’s vital that procedures for calling out bad behaviour internally must be trusted by officers in its ranks.”

Met Commissioner Dame Cressida Dick has defended the Met’s whistleblowing procedures in previous meetings of the London Assembly police and crime committee, having said that they are “quite actively used”.

But in a meeting at City Hall in November last year, Deputy Met Commissioner Sir Stephen House revealed that officers are not automatically entitled to anonymity if they blow the whistle on their colleagues for misconduct or inappropriate behaviour.

Speaking at the time, he said: “It depends on the circumstances. But frankly, it is their duty as a police officer to report that, so they wouldn’t get anonymity as an automatic case, and they may have to give evidence in court.”

Read more: Met launches Downing Street Covid breaches investigation

The London Assembly police and crime committee will on Tuesday grill Met Commissioner Cressida Dick over the findings of the Stephen Port murder inquest which found significant failings on the part of the Met, as well as the “partygate” scandal that has rocked the Government.

The meeting will take place at London Fire Brigade headquarters at 10am, and will be broadcast live on the London Assembly website.