Public complaints against Norfolk police officers - including allegations of serious and sexual assault - rose by more than 40pc last year, official figures reveal.

Public complaints against Norfolk police officers - including allegations of serious and sexual assault - rose by more than 40pc last year, official figures reveal.

The statistics highlight claims including 138 reports of assault between April 2005 and March 2006. Among these are three claims of sexual assault and one of serious assault all lodged in the first quarter of this year. The figures show 862 complaints compared with 607 in the previous year.

Other figures released yesterday under the Freedom of Information Act showed six police officers have been involved in criminal proceedings. One was convicted under the Data Protection Act, two cautioned for common assault, two for criminal damage and one convicted under the Wildlife and Countryside Act.

Force chiefs attribute the increase in complaints to better reporting procedures and increased awareness of human rights legislation. A police authority member also cited the rise of a US-style litigation culture.

A police spokesman said: "All constabulary staff and officers are subject to a strict disciplinary code and all complaints are treated seriously."

The most common complaints were neglect of duty issues, which include lack of thorough investigation and failure to update complainants.

Complaints involving attitude and behaviour; and assault, particularly the use of excessive force during arrest, were the next most common.

Her Majesty's Inspector of Constabulary rates the force as "good" in the way it handles and investigates complaints. The force exceeded government targets by resolving 51pc of complaints at a local level. Of the remainder, 1pc were substantiated.

Seven of these related to neglect of duty; two to excessive force during arrest; and three to breach of custody regulations. All other complaints were discontinued, withdrawn or found to be unsubstantiated. The force's Central Area - which includes Norwich - recorded the highest number of complaints.

There was a 69pc fall in discriminatory behaviour problems and none of the complaints received were serious enough to warrant action.

"Our officers deal on a daily basis with human temperament, often at times when members of the public find themselves in a crisis situation and feelings are running high," said the spokesman. "Misunderstandings can occur and complaints can fluctuate. At other times investigations can reveal errors of judgment and when this happens, we are prepared to admit we have made mistakes."

Other figures released yesterday showed 13 staff grievances were lodged in the last year, eight by officers and five by other staff. Seven of these related to behaviour and six to the application of policy or procedure. The majority were resolved by line managers.