Police have given a guarded welcome to proposals to change the make-up of England and Wales's 43 police forces.
The home secretary said he would consider cutting police forces
But the Police Federation has warned that merging smaller forces must be about efficiency, not cost-cutting.
In a report for the home secretary, the Inspectorate of Constabulary said the existing structure was "no longer fit for purpose" in the 21st Century.
However, a former chief constable of Gwent, Francis Wilkinson, questioned whether a change would be a benefit.
"The question really is, are these enormous savings that are proposed in this report real?" he told the BBC.
"What will be the costs of change? And are they really going to benefit the majority of people who use police services, who are local?"
Inspector of Constabulary Denis O'Connor, who is a former Surrey chief constable, criticised the number of forces currently in existence.
SMALL FORCES FACING REFORM
Home Office figures for March 2005
Norfolk - 1,554 officers
Suffolk - 1,323 officers
Cambridgeshire - 1,418 officers
Wiltshire - 1,228 officers
Dorset - 1,475 officers
Hampshire - 3,803 officers
Warwickshire - 1,012 officers
City of London - 881 officers
Dyfed-Powys - 1,183 officers
Gwent - 1,438 officers
North Wales - 1,676 officers
He said: "In the interest of the efficiency and effectiveness of policing it should change."
Mr O'Connor said forces with more than 4,000 officers tended to perform best and that reorganisation could save up to £2.3bn over 10 years.
At present, 19 have fewer than 2,000 officers - mostly in rural areas - with senior officers admitting that some struggle to meet the challenges of modern crime.
Home Secretary Charles Clarke said he would consider the report carefully before giving a response.
"I look forward to productive discussions on the best way forward," he said.
But, shadow environment secretary Oliver Letwin dismissed the proposals as "undiluted rubbish".
The MP for West Dorset said he did not want to see the Dorset force merged with Hampshire, as might happen.
"The big problem about policing in Dorset and I suspect it's very similar in most other counties in other rural England ... is the people feel the police are remote, we don't see them," he said.
"We used to have village policemen, we used to have policemen parading around towns, we see less and less of this and neighbourhood policing is what matters to most people because most people are most affected by very low levels of crime."
The Association of Chief Police Officers (Acpo), welcomed the report's findings.
Its president, Chris Fox, said: "All forces must have the capability to deal with terrorism, cross-border and international crime if we are to keep the public safe and give them the service they expect and demand."
But he warned restructuring would be "complex and expensive". He said Acpo and other policing bodies would be meeting the home secretary on Monday to discuss how to take the report forward.
However, some forces have expressed concern at the report's proposals.
Ian Roberts, chairman of North Wales Police Authority, said he did not want the four Welsh forces to be "lumped together" as his area would become "isolated".
He said: "Logistically, north Wales and south Wales are poles apart. We've got a large stretch of mountains between us and it takes three hours to get down there."
Alan Gordon, vice chairman of the Police Federation, told the BBC all the public wanted was a reliable service.
" Whatever comes out of this has got to be able to demonstrate that the net result is going to be a more effective service that the public will benefit from.
"What they don't want to see is change for the sake of change, change based purely for financial efficiency or some politically expedient demonstration of reform.
"What we want to see is a service that is going to be better equipped, better able to deliver a better quality of service to the public."
The five options set out in the report were:
Strategic Forces - Forces "re-grouped" so they "exceed critical mass", but this proposal could be perceived as the most disruptive and least "locally friendly".
Federal Structure - A "federation" of sub-standard forces would draw up their own plans to set up a number of central units to improve weak areas of policing. Existing force boundaries would remain.
Lead Specialist Forces - Certain forces given extra resources to take control of certain types of investigation across a wider area, although there may be a shortage of candidates and would not address all shortcomings.
Lead Regional Forces - One force in a region would take on back-room functions such as finance and personnel for a number of forces in the region, freeing them up to concentrate on local and cross-border crime.
Collaboration - Preserving roughly 43 forces and setting up more collaboration, although this would be "complex, slow and of limited impact".