The email was leaked as Mr Norris launched his poster campaign

As the election date of 10 June approaches, Scotland Yard is worried candidates will simplify crime figures due to be released next week.

In a leaked email, Sir John Stevens is said to be concerned that violent crime figures will be misinterpreted.

It comes as Tory candidate Steve Norris launches his poster campaign claiming crime has risen relentlessly.

The candidates, including current mayor Ken Livingstone, have had a preview of Home Office crime figures for London due to be published next Thursday.

They are believed to show a 19% increase in violent crime from 2000 to 2004.

But police say it is largely because they have encouraged more people to report crime, and the way it is recorded has changed.

Figures 'lead to confusion'

Deputy Assistant Commissioner Brian Paddick, who wrote the email to candidates, said police wanted to give Londoners a clear picture of crime in London.

He said: "If we have mayoral candidates using different sets of figures over different time periods, it's just going to lead to confusion.

"We want to have one set of agreed crime figures that all the mayoral candidates are using and also [make sure] that they understand what lies behind these figures."

Mr Norris agreed the message appeared to be aimed at him.

But he told BBC London he was prepared to "make trouble" and take the blame if Londoners did not think the city was more dangerous.

"I think Londoners are shrewd enough to work out who's right on this one," he said.