The majority of voters in parts of England and Wales where the government wants police forces to merge are opposed to the plans, a poll suggests.
It is thought 25,000 police officers' jobs may have to be axed
Just 36% of those surveyed for the Policy Exchange think tank supported the mergers, compared to more than half - 58% - who opposed the changes.
Proposals made by former home secretary Charles Clarke aimed to cut the 43 forces in England and Wales to 17.
Populus interviewed 4,569 adults for the survey between 26 April and 18 May.
The highest levels of opposition to the proposals were recorded in the East Midlands and the South-West - in which 60% were opposed - and East Anglia and the South-East - where the figure was 59%.
Meanwhile, the highest levels of support was in the West Midlands, where 40% favoured the plans, and the North-West, where 39% were in support.
The poll followed a Policy Exchange report, entitled Size Isn't Everything: Restructuring Policing in England and Wales, which argued that the planned mergers would prove unpopular and unworkable.
The report also concluded that there was no evidence that larger forces are more effective.
Those questioned who said they were aware of the mergers rejected them by a margin of more than two to one - 43% of the total against 20%.
London and Greater Manchester would be unaffected by the planned mergers, while Hampshire, Kent and Thames Valley would become "strategic forces" inside their existing boundaries.
However, all other services - with the possible exception of those in the South-West, where final plans have not yet been confirmed - would be merged into regional "superforces".
Police chiefs in Wales have threatened to pull out of the process of merging all four of the principality's forces, following consultation on the plans.
A financial forecast drawn up for the Association of Chief Constables predicted that 25,000 police officers' jobs may have to be axed to meet the cost of the restructuring process.
James O'Shaughnessy, Policy Exchange's head of research, said: "The results of our poll are unequivocal. The government's proposed police force mergers are unpopular in all the regions affected.
"The Association of Chief Police Officers is already making contingency plans to replace 25,000 police officers with community support officers to offset the £500m national cost of restructuring.
"Local residents know that merging police forces will mean fewer police, less accountability and less attention paid to local crime. Home Secretary John Reid must act to stop these plans now."
The Home Office made clear that it continued to back the principle behind police force mergers, but a spokesman said it had to communicate the "compelling reasons" for restructuring to the public.