Only 13 out of 43 police forces in England and Wales have expressed a desire to merge, says the Association of Police Authorities (APA).
The Home Office says mergers will help them tackle terrorism
Home Secretary Charles Clarke set a deadline of Friday for forces to present restructuring plans. He wants to merge the forces to as few as 12.
The authorities have "unanimously rejected" this, said the APA.
It says none are submitting full business plans before the deadline, but some are presenting detailed proposals.
Mr Clarke had given police forces until Friday to submit responses to a consultation on the police reform proposals.
The association claims none of the 43 police forces in England and Wales will be submitting a final business plan for mergers, as requested by the Mr Clarke, by the deadline.
The association's Bob Jones said: "Police authorities have unanimously rejected the home secretary's plans to force these proposals through with indecent haste, and we believe there are also credible alternative options which should be considered very seriously."
The BBC's home affairs correspondent Danny Shaw said 26 police authorities have expressed a clear preference (13 for merger, 13 to stand alone).
He said 17 constabularies have not decided or revealed their preference.
Danny Shaw said the figures suggest Mr Clarke will have a huge battle to drive through his reforms.
He said none of the merger plans put forward has the complete agreement of all the forces involved.
Suffolk and Norfolk want to amalgamate but they cannot agree whether Cambridgeshire or Essex should join them.
Yet Cambridgeshire and Essex are among 13 forces which want to remain separate.
A Home Office spokesman said the government had always accepted that meeting the deadline was "challenging".
"We will look in detail at the submissions we have received after Christmas, when we will also announce the timetable for taking this matter forward," he added.
"We recognise there will be a need for further discussions and we will be working closely with all police forces and authorities in January, including meetings with chief officers and police authority chairs to discuss the outstanding issues."
Earlier on Thursday it was revealed West Midlands, Staffordshire and Warwickshire forces all backed a four-way merger that was supposed to include West Mercia Police.
But West Mercia declined to sign up and wants to remain as a stand alone force.
Mr Clarke believes the force mergers will lead to more efficient police forcing, helping to combat terrorism and organised crime.
But in the Commons earlier this month his plans came under sustained attack from opposition MPs
Shadow home secretary David Davis warned the changes would mean a less localised service.
Mark Oaten, the Lib Dems home affairs spokesman, accused the government of carrying out a "rushed process".
The plans were announced after a report by Her Majesty's Inspectorate of Constabulary (HMIC) said forces with fewer than 4,000 officers were not equipped to fight sophisticated modern crime.