West Mercia Police Authority will decide this week whether to apply for a judicial review of plans to create a giant regional police force.

The Government already faces one legal challenge after Cleveland Police Authority, which faces being combined with Durham and Northumbria, announced yesterday it was to seek a review at the High Court.

West Mercia has asked John Reid, the Home Secretary, to give it further details of his plans. It will decide by the end of tomorrow whether or not to go to court.

Meanwhile four West Midlands' councils - Solihull, Birmingham, Coventry and Dudley - have jointly begun judicial review proceedings challenging the amalgamation of the West Midlands, Staffordshire, Warwickshire and West Mercia Police Authority areas.

They have complained there has been no proper consultation and that there has not been enough information provided on basic issues, such as finance.

They fear the proposed restructuring will lead to higher council tax bills, through precept equalisation. Currently the precept paid by West Midlands Council Tax payers is at a lower level than levied in the surrounding county areas.

As a result, residents in the West Midlands could face an increase of up to 40 per cent in the police precept.

Although the Home Office has indicated that there will be a phased approach to precept equalisation, no details have been made available, the councils claimed.

The four West Midlands districts seeking judicial review are now asking the courts to intervene so that the Home Secretary does not go ahead to make statutory orders in July.

The districts are seeking a further 12 month period to allow for a proper consultation with affected Councils on financial and governance issues before final decisions are made by the Home Secretary. The Home Office plan is also fiercely opposed by local MPs and by West Mercia's Chief Constable, Paul West.

Dr Reid has promised further consultation with forces, and may delay the mergers for up to 12 months.

A spokeswoman for West Mercia Police Authority said: "West Mercia Police Authority has sought additional information from the Home Secretary to enable it to prepare a fully worked up objection to the proposed amalgamation order.

"This information has not been received and the Police Authority has until June 2 to decide whether it wishes to make an application to the Administrative Court to seek permission to judicially review various decisions that have been made by the Home Secretary in this process.

"The Police Authority's decision will be based upon any information that may be received from the Home Office prior to Friday."

Dave Mcluckie, chairman of the Cleveland Police Authority, said he had tried to meet Dr Reid to discuss the plans, but this had proved impossible.

"We want to actually find resolution to this that didn't include court action. That hasn't been the case," he said.

But a Home Office spokeswoman said it was "premature" to seek a judicial review against the mergers, as the Home Secretary would not be making any decision on the plans until he had considered all views.