Official figures released on Thursday revealed there were more than 22,000 serious offences in England and Wales involving knives in 2007-8 but overall crime fell significantly.

Knife crime has become a top political issue in recent weeks with 20 teenagers dying in violent attacks, mostly stabbings, on the streets of London so far this year.

For the first time, the government released figures about serious crimes where knives had been involved after police were asked to change the way they collected data.

This showed there were 22,151 such offences in England and Wales in the year up to March 2008, with all areas including those covered by more rural forces being affected.

There were nearly 7,500 knife-related offences in London - the highest number - with the lowest number, 613, recorded in the northeast.

"Because this is the first time we have such data this says nothing about the trend in such crime," said the Home Office's Scientific Advisor Paul Wiles.

"We will only be able to talk about trends when we have data over a longer time period."

Criminologists believe there has not been a dramatic increase in knife crime, but that the profile of the offender and the victim has become younger.

"We've identified the problem of knife crime particularly in some hot spots of the country," said Prime Minister Gordon Brown.

"We've stepped up our action dramatically - more stop and search, more visible policing and tougher sentences. I want the message to go out that knives are unacceptable - there are borders that you cannot cross."

The government pointed to figures from the British Crime Survey, (BCS) based on interviews with the public, which showed total violent crime was down 12 percent while the risk of being a victim had fallen from 24 percent to 22 percent.

This is the lowest figure since the BCS began in 1981.

"Whilst the BCS shows violence falling by 40 percent since 1997, with a 12 percent fall in the last year alone, we also know that knives are still being used in the most serious violent incidents," said Home Secretary Jacqui Smith.

According to the BCS, crime fell by 10 percent while police figures indicated it was down 9 percent.

"The fall in crime over the last decade mirrors what is happening in other western developed economies," added Wiles.

"That has largely been a period of economic growth but it has also seen the introduction of anti-theft devices. The biggest single drop has been in car theft. It's much more difficult to steal a car than it was 25 years ago."

Given the fragile state of the economy, Wiles forecast that the credit crunch could see an increase in property crime.

With five million crimes committed last year, gun crime was up two percent, murder rose three percent, while there were 2.7 million fraudulent credit card transactions, a 20 percent increase.

Drug offences also showed a dramatic increase - 18 percent - with Wiles attributing that upsurge to the extent of police targeting narcotic activity.

The BCS has been criticised in the past because it does not include under 16-year-olds. Their views will be included next year.