Little faith in crime stats - Blair

The New Scotland Yard head said the way crimes are categorised has been changed "so frequently they are bewildering".

He suggested that British authorities adopt the same system as in New York where crimes are recorded in a more straightforward way.

Speaking at the second Colin Cramphorn memorial lecture at the Policy Exchange, Sir Ian said the media and politicians have also weakened confidence in crime statistics.

He said: "Few question the crime figures in New York. Residents largely accept that their city is safer than it was. And that is because New York has not fiddled about with how they collect crime statistics in the way the UK has."

Sir Ian said many people would be surprised at how many crimes are recorded and said, for example, that gun enabled crime until recently included attacks with CS gas.

He mocked a definition of knife crime provided for police which includes an exhaustive list of weapons such as machetes, axes, crossbows, darts and needles.

He said: "...then is added, in a rather Monty Python way and I quote again, 'this list is not meant to be exhaustive', presumably in case someone is stabbed to death with a cocktail stick."

Sir Ian called for crime counting rules to be revised and simplified to make figures simpler and more credible. He said a similar transformation to New York policing has been taking place in London but in a "rather unstated British way".

Sir Ian said the Metropolitan Police welcomed plans by new Tory Mayor Boris Johnson to introduce New York-style crime mapping. He said: "But it would help if the data that made up the map were of a sort that fully makes sense."