Inspectors said senior officers at North Yorkshire Police needed to act "urgently" to help victims and families affected by violent and serious offences.

They found that the force was also failing to collect information and to develop tactics to combat major crime.

Cumbria, Lincolnshire and City of London, Cheshire and Wiltshire Police were the other forces identified as falling below national standards in the report, published by Her Majesty's Inspectorate of Constabulary (HMIC).

HMIC head Denis O'Connor said: "This report shows that while the police response to homicide is improving, some forces in England and Wales are still failing victims and families affected by major crime, and must improve their services.

"The public rightly expects their local police service to protect them from serious harm and respond professionally when tragic events occur.

"While most forces can and do meet that expectation, some cannot. This needs to change."

HMIC officials inspected all 43 forces in England and Wales between July and September last year.

Their findings were published only a fortnight after North Yorkshire detectives were accused of not acting swiftly enough by friends of Miss Lawrence, who disappeared from York four months ago and is thought to have been murdered.

The force is also investigating the murder of Cai Guan Chen, whose beaten body was found in a canal near Selby in March.

Acting assistant chief constable Steve Read said the report was based on evidence gathered almost a year ago and added that the force was now working with West Yorkshire, South Yorkshire and Humberside Police to tackle serious crime.

"The two large-scale murder inquiries...are prime examples of practical regional collaboration with detectives and uniformed officers from all four forces being significantly utilised in the pursuit of both inquiries," he said.