Leading article: What the Metropolitan Police needs from its new chief

Something is plainly rotten at Scotland Yard. The Metropolitan Police force has been responsible for a catalogue of blunders in recent years, from the mistaken killing of Jean Charles de Menezes in 2005 to the clumsy arrest of the Conservative immigration spokesman Damian Green last month.

This sorry list of foul-ups was added to at the weekend by an outburst from the counter-terrorism chief, Bob Quick, who accused the Conservative Party of planting embarrassing stories about him in the press. It turned out that Mr Quick had not bothered to check whether this was true or not when he argued that the Tories were guilty of "spiteful" and "corrupt" intimidation.

The Conservatives accepted Mr Quick's shamefaced apology yesterday, but it is hard to see how someone who has demonstrated such a crashing failure of judgement can remain in charge of a brief as sensitive as anti-terrorism policing. And it is simply impossible to see how Mr Quick can continue to head the ongoing investigation into Mr Green, which he was responsible for sanctioning.

Yet there are deeper problems within the Met than the flawed judgement of a single officer. The sheer number of mistakes and scandals that have engulfed the force of late indicates a dysfunctional organisation. It also indicates a chronic absence of effective leadership.

Sir Ian Blair has a lot to answer for. The former Met Commissioner resigned last month, after London's Mayor, Boris Johnson, withdrew his support, warning of the dangers of political interference in policing. But Sir Ian was no innocent victim of political intrigue. His downfall was rather a consequence of his own inept attempts to play politics with his office. Sir Ian spent a considerable amount of time putting out fires that he himself had started. And he neglected his primary responsibility of ensuring that the capital's police force was well organised and competent in its work.

Mr Quick's blunder underlines the need for the Home Secretary, Jacqui Smith, to make the right choice over Sir Ian's replacement. The candidates believed to have made it on to the short list are Sir Paul Stephenson, the Acting Commissioner of the Met, Sir Hugh Orde, the chief constable of Northern Ireland, Sir Paul Scott-Lee, the chief constable of the West Midlands, and Bernard Hogan-Howe, the chief constable of Merseyside.

The new Commissioner of the Met will face several pressing tasks. They will, first of all, have to convince Londoners that the Met will be a competent and effective crime-fighting force. A specific concern for many Londoners is the prevalence of teenage knife crime. Recession is only likely to make the job of maintaining law and order in a chaotic capital more difficult, so the new boss will need to be right on top of the operational agenda from the outset.

The new Commissioner will also need to answer to a Labour Home Secretary and a Conservative London Mayor. In that respect, the job is inescapably political and demands a deft candidate able to walk that tightrope. Finally, the new Commissioner will need to win back the support of the Met rank and file, while continuing the good work of Sir Ian in increasing levels of ethnic minority representation in the force.

The Met needs a leader, a diplomat and a crime fighter. It is a tall order. We must hope that there is someone on the shortlist able to demonstrate that they are up to the most challenging job in policing.