The London mayor, Sadiq Khan, has warned the candidates wanting to lead the Metropolitan police they must publicly admit the force’s systemic failings, with formal interviews due to begin next week.

Two senior police figures have reached the final stages of the process to be the commissioner of Britain’s biggest and most controversial force.

Khan used a speech to stress he would not support any candidate who did not commit to sweeping reforms.

As well as being the mayor, Khan is the elected police and crime commissioner for London. The head of the Met is formally appointed by the home secretary, who has to have due regard to the views of the mayor.

In practice, if the mayor declares he does not have confidence in a Met commissioner, they are expected to resign. In February Cressida Dick resigned after falling out with Khan, who was unconvinced she could turn the Met around after a series of scandals.

Khan said in his speech: “I want to make crystal clear today I won’t support the appointment of a new commissioner unless they can demonstrate they understand the true extent of the cultural and organisational problems within the Met.

“That they appreciate the moral and operational imperatives to confront them head on and that they have a convincing plan to reduce crime further, improve detection rates and bring more criminals to justice.”

The advert for the commissioner’s job, which was issued by the Home Office and the London mayor, made clear the need for radical reforms. After Khan’s speech government sources said there was little or no difference between the Conservatives and the Labour mayor on the need for an overhaul of the Met.

The candidates will be grilled next week by a panel chaired by Matthew Rycroft, the permanent secretary at the Home Office, and including the former chief inspector of constabulary Sir Tom Winsor and a senior official from the mayor’s office.

Going before them will be assistant commissioner Nick Ephgrave, who was in the Met’s senior leadership from 2019 as a series of scandals unfolded.

He will have to convince the panel he can reform the culture of the force. After a serving Met officer was jailed in September 2021 for the kidnap and murder of Sarah Everard, Ephgrave said women anxious about a police officer who approached them on a street could wave down a bus. He did add the scandal meant the Met needed to “examine our own culture”.

The strong frontrunner is Sir Mark Rowley, who in 2018 left the Met having served as an assistant commissioner in charge of counter-terrorism. While in the force he impressed some with his calmness under the pressure of the wave of terror attacks in 2017. Before that role, he had backed the attempt for the Met to use water cannon to douse crowds.

Both candidates were previously chief constables of Surrey police, and regarded as able by policing colleagues.

In his speech Khan stressed the majority of Met officers did a great job, as he tried to deflect claims political manoeuvres by himself were damaging the force. “It’s not being political. It’s democracy in action. It’s the checks and balances of power, without which we’d still be living with the kind of policing we saw before the Stephen Lawrence inquiry,” he said.

The string of crises and dissatisfaction has led to a haemorrhaging of public confidence in the Met, according to polling conducted for the London mayor. The current Met leadership believe other polling has showed the public is happier with them. Multiple sources say the Met’s senior leadership believe the treatment of the force and its leadership has been unfair.

The Conservative government deterred assistant commissioner Neil Basu from applying, believing he was too outspoken on issues such as racial justice. Basu was seen as the frontrunner and would have been the first minority ethnic Briton to lead the Met. He was then also blocked from leading the National Crime Agency.

The panel interviews for the Met commissioner job will be followed by further grillings by the home secretary and Khan. The policing minister, Kit Malthouse, may also interview the candidates, and it is an open secret Downing Street, despite having no formal role, will also approve the choice of the next commissioner.

No decision is expected until July and the commissioner is technically appointed on a royal warrant by the Queen.