The number of regional police forces in England and Wales could be cut from 43 to just 12 under new proposals announced by the home secretary.
Charles Clarke said the plans were necessary for police to face the modern threats of terrorism and international organised crime.
The proposals follow a report by HM Inspectorate of Constabulary (HMIC) in September, which said the current police structure is no longer able to provide effective community policing and deal with serious cross-regional crime.
It found that neighbourhood policing in forces with fewer than 4,000 officers or 6,000 staff would inevitably suffer in the event of a major investigation, with resources diverted away from local services.
"The changing nature of crime poses a significant challenge for the police," Mr Clarke said.
"The modern threats we face from terrorism and international organised crime do not respect established local borders. We need police forces with the resources and capabilities to prevent and act against serious crime."
He said the proposals, which would create a "strong strategic force" while keeping a local basic command unit for community policing, had been put forward following submissions from the police themselves.
However, the Conservatives rejected the plans - which would result in the creation of just one police force in Wales, where four currently exist, and just one in the north-east to replace the existing three.
"Replacing the current structure with regional police forces will seriously damage the relationship between local areas and their police," said shadow home secretary David Davis.
"As the bonds between communities and their police forces disappear, local accountability will be eroded.
"What we want to see is local communities having a genuine connection with their police forces. This will not be achieved through regional policing and we will fight it."