Home Secretary Charles Clarke has outlined plans to merge several police forces in England and Wales.
Mr Clarke will meet with police chiefs affected
It would create a single force for Wales and would also affect the North West, North East and the West Midlands.
Tony Blair has pledged not to "force through" merger plans, but ministers insist bigger forces are now needed.
The Association of Police Authorities says forces should work together on such issues as fighting terrorism and organised crime, rather than merge.
Home Office Minister Paul Goggins has suggested the plans could mean some people paying higher council tax bills.
The government will invest £125m towards the merger costs but once that was spent, extra money would need to be found locally, he said.
The extra sum added to council taxes for policing would need to be "equalised" when different forces merged, he said.
Merging forces named
Under Mr Clarke's proposals, a new larger West Midlands force would be created with the merger of Staffordshire, Warwickshire, West Mercia and West Midlands.
Cleveland, Durham and Northumbria would become a North East force. In the North West, Cheshire and Merseyside would merge and Lancashire and Cumbria would join together, and in Wales, all Welsh forces would merge.
Mr Clarke's conclusions are based upon options submitted by forces themselves in last year's consultation period, which have since been looked at by Her Majesty's Inspectorate of Constabulary (HMIC).
The HMIC had said forces with fewer than 4,000 officers were not equipped to fight sophisticated modern crime.
In a written statement to the Commons, Mr Clarke said merging forces in these areas was the "one acceptable option".
Talks were held at the Home Office on Monday on how best to implement these proposals with chief constables and police authority chairs of all the affected forces.
Discussions about changes in five more regions will proceed in the next few weeks.
Last month Mr Blair said that some forces might not have to merge and he promised to listen to opposing views on the issue.
He said the proposals had been prompted by the Association of Chief Police Officers which had argued that the current configuration of forces "was not satisfactory in fighting crime".
However, Association of Police Authority (APA) chairman Bob Jones said merger costs could reach £1bn.
The APA said 13 forces had expressed a desire to merge, 14 wanted to "stand alone", and the remaining 16 had no preference or were undecided.
It argues that many prefer a "federated" approach, where neighbouring constabularies work together to deal with cross-border crime, serious incidents and roads policing.
But Mr Clarke does not think that approach will work and says larger strategic forces will help combat terrorism and organised crime, as well as improving neighbourhood policing.
Council tax bills
The Conservative's shadow police reform minister, Nick Herbert, said: "Regional forces covering up to 6,000 square miles will erode local accountability, and most of the £175 million cost will be met by local people, adding up to £33 to council tax bills."
Mr Herbert said it would have been cheaper and less disruptive to have forces sharing services.
He said: "The fact that North Wales police are not being allowed to consider merging with an English force, even though crime patterns would dictate that option, betrays the government's true regional political agenda.
"The creation of a West Midlands force isn't a merger - it's a hostile takeover of West Mercia police, one of the top ranked forces in the country, which wants to stand alone."
Barbara Wilding, chief constable of South Wales Police, said she was in favour of the merger.
"Operationally, it makes absolute sense that we should have integrated all our intelligence, all our structures, all our training," she said.