Four local forces would become one under the plan

West Mercia Police Authority, which covers Herefordshire, Worcestershire and Shropshire, has said it is "strongly opposed" to a merger plan.

It would join the Warwickshire, West Midlands and Staffordshire forces to create a "super-force" for the region.

The Home Office has said it is premature to seek a judicial review.

The merger is part of a national plan which would reduce the number of forces from 43 to 24. The Home Office has said larger forces are needed to better tackle organised crime and terrorism.

West Mercia's High Court bid follows one from the North East authority Cleveland, which opposes merging with two other forces, and one from four councils in the West Midlands which are concerned about a rise in council tax.

The people in the area simply do not see a huge regional police force as an attractive proposition Paul West, Chief Constable West Mercia Police

Paul Deneen, chairman of West Mercia Police Authority, said there had been poor consultation from the Home Office and there would not be enough time to prepare for the planned merger.

"It is wholly unrealistic, unnecessary and unacceptable to expect this rushed and untested model of policing to be forced upon the communities of West Mercia."

He said he hoped a judicial review would allow a "thorough examination of the process behind the merger proposals."

Staffordshire, West Midlands and Warwickshire forces are in favour of the merger.

But MPs from rural areas have voiced fears that the merger could see resources diverted to bigger cities, where crime rates are higher.

Paul West, chief constable of West Mercia, said the force was not opposed to change but any major change should be well planned and open to wide-scale public debate.

He said people living in Shropshire, Herefordshire and Worcestershire did not support the merger.

"The people in the area simply do not see a huge regional police force, delivering services across five counties and the West Midlands conurbation as being an attractive proposition."

A Home Office spokeswoman said: "The Home Secretary will not make a final decision on whether to proceed with the merger until he has carefully considered any objections received.