AT LEAST one police officer is attacked on duty every hour while the number suffering serious injury is soaring.

More than 500 officers were seriously injured last year - up by a fifth in just two years, Home Office figures show.

And separate statistics revealed the number of officers injured or killed by a firearm has rocketed by 250 per cent since 1997.

It came as the number of full-time police officers in England and Wales fell once again, while the number of civilian "plastic bobbies" increased by 17 per cent.

Rank-and-file leaders yesterday warned the true picture of violence was even higher as many officers did not report minor injuries or assaults. They said Home Secretary Jacqui Smith's refusal to back down in the pay row earlier this year was even more insulting in view of the growing risks faced by officers.

Simon Reed, vice-chairman of the Police Federation, said: "We're convinced there is under-reporting among officers, many of who will not report a minor assault.

"It is interesting to see politicians at police bravery awards say how proud they are but they are obviously not proud enough that we receive what we deserve from last year's pay award."

There were 11,392 assaults, both injury and non-injury, on police officers in 2007/08 - the equivalent of 31 a day.

While that total was a slight decrease on recent years, officers suffering serious injury is on the rise. A total of 502 were seriously injured on duty last year compared to 423 in 2005/06 - an increase of 19 per cent.

But a study last year suggested as many as 70 officers a day are being assaulted.

Mr Reed accused many forces of not carrying out sufficient self-defence training and called on police chiefs to improve standards.

Separate figures obtained by the Shadow police reform minister David Ruffley also showed 21 officers were shot or injured by a firearm in 2006/07 - a huge increase on the six who were injured in a similar way in 1997/98.

Annual police strength statistics yesterday showed there were 141,859 full-time officers in England and Wales at the end of March - 33 officers less than last year.

Under an old measure, which does not take account of those on career breaks or parental leave, there was a decrease of 304 full-time officers year-on-year to 139,728.

Shadow Home Secretary Dominic Grieve said: "These statistics suggest that we have reached the tipping point and police numbers are set to continue to fall."

Lib Dem home affairs spokesman Chris Huhne said: "High-visibility policing is already hampered by red tape and central targets, without being further eroded by reduced manpower."

But Home Office minister Tony McNulty said: "Police officer numbers remain historically high. There has been an additional 14,000 officers recruited since 1997."