Small police forces such as the Warwickshire, Staffordshire and West Mercia constabularies must be saved, Liberal Democrats vowed yesterday.
Home Affairs spokesman Mark Oaten attacked plans to force smaller forces to merge, at the party's annual conference.
All forces with fewer than 4,000 officers are under threat, after a review of police services concluded they were incapable of dealing with modern crime.
Small forces lacked the ability to gather intelligence, tackle terrorist threats and deal with complex fraud inquiries, a report commissioned by the Home Office said.
Charles Clarke, the Home Secretary, responded by announcing a major shake up of the nation's police.
Three of the region's forces are directly affected, because they have so few officers.
The fourth, West Midlands Police, might also be affected if it is told to merge with a smaller force.
But Mr Oaten yesterday launched a campaign to save shire forces.
He said: "We should be making them more local, not more distant.
"People want to have the confidence that police know the area, that Chief Constables will visit and know every town and village in their area.
"So we say keep the forces as they are but provide a national resources unit with senior officers and experts to provide back up in complex cases.
"So Home Office - hands off our local forces. Let's keep them as they are. Let's go out and campaign to keep our local forces."
Mr Oaten also revealed his party would refuse to support Mr Clarke over some of the Government's proposed anti- terror legislation.
The Lib Dems would back laws making it an offence to train terrorists, to prepare for a terrorist attack or to incite terrorist activity, he said.
But they would oppose what he called "a wide and vague offence" that made glorification of terror a crime.
It was a "dangerous" proposal which would never work because it was impossible to define what glorification meant, he said.
He also attacked proposals to allow people to be held for three months without charge.
He said: "If we abandon traditions and values like the right to a fair trial, we are abandoning our identity."