A proposed merger of West Midlands Police with neighbouring forces has been condemned by Conservative leadership candidate David Cameron.
He said the public wanted more local policing - and not a remote new constabulary.
Mr Cameron was in the Midlands to meet activists as part of his campaign.
West Midlands Police could be merged with West Mercia Police, Staffordshire Police and Warwickshire Police as part of a major shake-up of the nation's forces.
The Home Office says smaller forces do not have the resources to tackle organised crime and terrorism.
But the idea of a huge regional body, stretching from Worcester to Stoke, has been criticised by some MPs.
Paul West, Chief Constable of West Mercia Police, told Ministers it was the "wrong model" for the region, in a meeting in Westminster.
Mr Cameron, speaking in Ludlow, Shropshire, pointed out that West Mercia had already been revealed as the best in the country in an official inspection.
He said: "West Mercia force has a good record and the case for a regional force simply has not been made.
"What people want to see is more local policing." A second option being considered by the Home Office is to create two forces by merging West Midlands Police and Warwickshire Police, and West Mercia Police and Staffordshire Police.
MP Philip Dunne (Con Ludlow), a Cameron supporter, said: "I am most grateful to David Cameron for meeting so many Members in Ludlow where he has strong support.
"His backing for the campaign to ensure survival of West Mercia as a strategic police force is very welcome."
Under Mr Clarke's proposals, Britain's 43 forces could be merged into just ten.
It follows a review by independent watchdog Her Majesty's Inspectorate of Constabulary, which warned smaller forces with fewer than 4,000 officers lacked the resources to deal with modern threats.
But MPs campaigning against the possible merger received a boost when a Home Office report identified West Mercia as the best force in the country.