Ministers have been urged to study research by Warwick University which could save Britain's best police force.
Academics claim there is no evidence that smaller forces, such as West Mercia Police, Staffordshire Police and Warwickshire Police, are incapable of protecting the public.
Ministers have ruled that forces with fewer than 4,000 officers cannot continue as they are, because they lack the resources to deal with organised crime and terrorism.
This is likely to lead to the creation of a giant regional force, merging the three smaller forces and West Midlands Police.
But West Mercia Police, which was named the best constabulary in the country by inspectors, is fiercely opposed to the proposals.
The force commissioned Professor Tony Lawrance, of the Department of Statistics at the University of Warwick, to examine the Government's proposals.
In a report sent to Home Secretary Charles Clarke yesterday, Prof Lawrance warned there was no clear relationship between the 4,000-officer size limit and the ability of police forces to provide effective services.
Even with 4,000 officers there would still be "an unknown number of good and poor performers," he said.
In a House of Commons debate, MPs urged Ministers to study the findings.
Owen Paterson (Con North Shropshire) said: "Already in West Mercia, we have a force that is going ahead towards strategic status on its own, backed by the remarkable analysis today from Professor Lawrance, statistics professor at the University of Warwick.
"He comprehensively rubbishes the statistical basis of the 4,000 figure."
And Peter Luff (Con Mid Worcestershire) said: "The whole statistical basis . . . is fundamentally flawed, and the 4,000 figure has no justification in empirical fact."
But Home Office Minister Hazel Blears was dismissive, and urged the MPs to read a Home Office report based on an inquiry by the independent inspector of police forces, which she said backed up the 4,000-officer minimum.
The proposed mergers were also criticised by Sir Patrick Cormack (Con South Stafford-shire) who claimed the consultation process had been rushed.
He told the Home Secretary: "He is driving fast and furiously without any regard to local concerns and local people."
But Pat McFadden (Lab Wolverhampton South East) backed the reforms.
He said the public needed police forces capable of dealing with a range of problems "from anti-social behaviour in local neighbourhoods to major organised crime such as drugs, people trafficking and, ultimately, international terrorism".
He added: "The easiest option would be to do nothing - to duck the issue, avoid the controversy, and say it was all too difficult."
He said Paul Scott-Lee, the Chief Constable of West Midlands Police, had told him the reforms would be good for the people of the West Midlands.
Adrian Bailey (Lab West Bromwich, West) said: "If both management and practitioners at local level are in favour of the reforms, there must be something going for them." ..SUPL: