The report, by Her Majesty’s Inspectorate of Constabulary, will be used by Charles Clarke, the Home Secretary, to press for the biggest reforms to the police in modern history, including a large reduction in the existing 43 forces in England and Wales.

Most forces in England and Wales were not devoting sufficient resources to fighting organised crime — described as “widespread, vibrant and growing” — and hard-drug abuse, the report said. It further found that only a few forces met required standards in dealing with big terrorist and public order incidents, and that the situation was worsening.

The study by Denis O’Connor, who is one of Her Majesty’s Inspectors of Constabulary, is blunt in its assessment of the capabilities of most forces. He said that only those forces that had more than 4,000 officers tended to perform best when judged against seven criteria.

Only seven forces in England and Wales have such numerical strength, and 19 have fewer than 2,000 officers. This suggests that 35 forces could disappear as either leading police officers or the Government push through mergers.

“Put simply, the 43-force structure is no longer fit for purpose. In the interest of the efficiency and effectiveness of policing it should change,” Mr O’Connor’s report said. “Our conclusion is that below a certain size there simply is not sufficient critical mass to provide the necessary sustainable level of protective services that the 21st century increasingly demands.

“The findings are stark — very few forces assessed fully meet the required standard.”

The study accuses the Home Office and police service of shying away from radical change over the past five years for fear of disrupting the fight against crime. As a result weaknesses in providing protection to the public in key areas had worsened.

It expresses alarm at the extent of organised crime in England and Wales and the many gaps in intelligence on large criminal enterprises and where they operate.

Smaller forces could have as few as seven or eight officers investigating serious and organised crime, the report found. “Despite best intentions these teams can quickly become swamped and are unable to deal with anything other than reacting to operations one at a time, leaving little or no time to develop intelligence.”

A significant number of forces in England and Wales were also reluctant to seek intelligence proactively on serious crime, particularly where drugs were not involved. Unless the gaps were closed it was only a matter of time before vulnerabilities were exposed, putting the public unnecessarily at risk.

Most forces would also have difficulty dealing with a terrorist attack or other incident of extremism. Some would only cope for a few hours while others could manage for between three and four days.

But no force could deal with simultaneous attacks at different sites without urgent help from neighbouring forces, as the Metropolitan Police did after the July bombing.

The largely county-by-county structure in England and Wales has traditionally been seen as a crucial component of the way police officers work with the consent of the public. Observers also say that it is an important safeguard against central political control of policing.

Mr O’Connor favours two options: the creation of strategic forces involving the merger of existing ones, or a federal structure in which sub-standard forces would set up central units to improve weak areas.

The most likely candidates for merger are thought to be those of Norfolk, Suffolk and Cambridgeshire, to form an East Anglian force; a combination of Wiltshire and Dorset, possibly with their larger neighbour Hampshire; merging the smallest county force, Warwickshire (1,012 officers), with a larger neighbour, possibly the West Midlands; and a significant reorganisation in Wales. The other forces with fewer than 2,000 full-time officers are Bedfordshire, Cleveland, Cumbria, Durham, Gloucestershire, Lincolnshire, Northamptonshire, North Yorkshire, and Surrey.

David Davis, the Shadow Home Secretary, said: “We will study this report carefully, but the Government must not use it as a backdoor method of transferring more police power to Whitehall.”

The Police Superintendents Association welcomed Mr O’Connor’s report. Rick Naylor, president of the association, said: “He says the 43-force structure is no longer fit for purpose — we have been saying that for some time . . . We have had this structure since 1974 and times have changed.

“When you think back to Soham and how poor old Cambridgeshire struggled, they had to get assistance from right across the country.”

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