Chief constables have said that they are “incensed” by a Tory advertisement placed in local newspapers in key marginal seats to suggest there has been a huge rise in crime since Labour came to power.

The row came as the Tories revealed proposals for a crackdown on yob culture, in which Mr Howard pledged to “wage a war” on thugs.

Police chiefs led by Richard Brunstrom, Chief Constable of North Wales, said that the Conservatives had used accurate but incomparable data to show soaring crime rates.

In 1999 an attack on three people would have been recorded as one crime. But under a new victim-focused system for recording the data introduced two years ago, they are recorded as three crimes. A push to record domestic violence and low-level thuggish behaviour more accurately has also driven up the numbers.

“This misleading advert quite improperly seeks to stir up fear of rising crime when it is a well-established fact that crime has been falling for years, both locally and nationally,” Mr Brunstrom said.

A report on Channel Four News said that six other police chiefs had complained about the selective use of data.

Conservative officials said they had adjusted the data to reflect the new methodology along the lines suggested by the Government, and refused to back down on their claims.

Labour said that the Tories had been caught red handed in running Britain down.

In his “war on yobs” pledge, Mr Howard said that thugs would live in fear under the Tories. He wanted the police to stand up to yobs, “eyeballing” them and “invading their personal body space” in confronting them on the streets.

He said that every force would have to publish weekly crime statistics on the internet.

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