MP Barry Sheerman has launched a campaign to oppose any merger of Huddersfield and Dewsbury police divisions.
He says such a merger would be an ``absolute disaster".
The Huddersfield Labour MP is contacting Home Secretary David Blunkett about the issue.
Police are conducting a review of policing in Huddersfield and Dewsbury.
But Mr Sheerman said: "I am very, very worried that these proposals to combine Huddersfield and Dewsbury police into one division will be an absolute disaster for our area."
A fight broke out at the Easter Fair in St Andrew's Road, Huddersfield on Sunday night and continued at Huddersfield Royal Infirmary, when casualties were taken there.
But Mr Sheerman doubted whether the police would be able to respond to incidents such as this after the amalgamation.
He said: "Huddersfield is one of the biggest divisions in the country and I believe it will be impossible to run as effectively as our division is now.
"Huddersfield and Dewsbury are very different communities and very often need a different touch in terms of appropriate policing."
Mr Sheerman is writing to Her Majesty's Inspectorate of Constabulary and to the West Yorkshire Chief Constable Colin Cramphorn to oppose any amalgamation moves.
Mr Sheerman added: "It is vital that people write before June, either to their MP, Mr Cramphorn or to the Home Secretary.
"Let's get a really good campaign going.
"The decision has not yet been made. Her Majesty's Inspectorate is looking at it.
"We need a good head of steam from the public who want policing to remain in Huddersfield.
"Bigger does not necessarily mean more effective or better local policing.
"We can still weigh in to make sure that we retain Huddersfield and Dewsbury as distinct units .
"We still have time to make a difference."
A West Yorkshire police spokeswoman vowed no police stations would close if the two divisions merged.
She said: "The Best Value process was designed by the Government to test and develop local public services, including policing.
"The review team looking at policing arrangements in Kirklees has yet to conclude its internal discussions, but the process requires us to consider all reasonable options.
"The option for one divisional headquarters rather than two leaves all existing police stations open, but changes the management structure and cost base."
* People can write to Colin Cramphorn QPM, Chief Constable of West Yorkshire Police at West Yorkshire Police Head- quarters, PO Box 9, Wakefield, WF1 3QP.
Alternatively write to Chief Inspector HM Inspectorate of Constabulary, at 50 Queen Anne's Gate, London, SW1H 9AT.