PUBLIC confidence in crime statistics took a fresh blow last night after the Home Office admitted police have failed to accurately record serious violent crime.

Some forces may have been misreporting the figures for more than 10 years, officials said, as they announced an annual increase in violent attacks of one-fifth.

Merseyside and Cheshire constabularies confirmed last night they were not one of the forces in question, although Lancashire Police declined to comment.

Months after the problem emerged, some forces were unable to provide updated figures, meaning the full extent of the most serious violent crime is not known.

Ministers said two-thirds of the increase in serious assaults could be explained by officers putting them in a lower cate-gory of offence. But only one third of serious knife attacks – which shot up nearly 30% – could be put down to reporting errors, officials said. That revelation will call in to question the success of high- profile attempts to tackle knife crimes and add to public fears of knife attacks on children follow-ing a string of high-profile deaths. The Home Office asked 18 forces to re-examine their statistics after the problem emerged but only 13 were able to provide accurate information.

The Home Office refused to name forces involved, but an investigation has established the Metropolitan Police was one of five which did not submit new data. The country’s largest force has suspended publishing some data as officials sort out the problem.

Others who were not record-ing crime accurately include Humberside, Derbyshire, North Wales, Cambridgeshire and Thames Valley.

Senior officers have not com-plained about how the rules were set out, but sources said they “required clarification”.

A senior Kent officer wrote to the Home Office to “express concern” at changes to the way crime figures are recorded and reported, a spokesman for the force said.

Shadow home secretary Dominic Grieve said the figures “fatally undermined” claims violent crime was getting better.

“Labour’s target-driven approach has simply been to manipulate statistics. They should face up to the reality of their failure and realise that if you can’t count a problem, you can’t combat it..”

Liberal Democrat home affairs spokesman Chris Huhne called on ministers to release the names of the 13 “so that local people are aware of wheth-er under-reporting happened in their area”.

Police Minister Vernon Coaker said the “clarification” did not mean the Government had lost faith in crime statistics and said he was being “up front” by revealing the problem.

“I would be embarrassed if I wasn’t coming forward . . .

“I want the statistics to be as accurate as possible. We have every confidence in the crime statistics.”