Home Secretary Charles Clarke will press ahead with the merger of Wales' police forces despite objections from all four police authorities.
Charles Clarke confirmed that Wales' four forces would merge
In a Commons statement, Mr Clarke gave chief constables, police authorities and councils until July to object.
He said many of England and Wales' 43 forces should merge by April 2007.
North Wales Police Authority expressed disappointment. The Gwent authority said it now accepted Mr Clarke had the ability to deliver the reorganisation.
The merger of Wales' four forces - South Wales, Dyfed-Powys, North Wales and Gwent - have been mooted since the publication of a HM Inspectorate of Constabulary (HMIC) report in September 2005.
The report proposed sweeping changes to the make-up of police forces in Wales and England stating that the current structure was "no longer fit for purpose".
Earlier this year, Mr Clarke announced that the UK Government planned the merge Wales' four forces and gave police chiefs until 24 February to agree.
The deadline passed with all four police Welsh authorities opposing the plans over issues such as funding and community policing.
But in his statement on Friday, Mr Clarke said: "The current 43 force structure in England and Wales has been in place for some 30 years.
"Much has changed in society since then and it is my responsibility as home secretary to ensure that the arrangements for policing are such that the current challenges can be tackled effectively.
Wales will now have a single force by April next year
"For Cheshire and Merseyside and the forces in the North East, West Midlands and Wales, I am satisfied...that it would be in the interests of the efficiency and effectiveness of policing for the forces in each of these areas to merge."
He gave police authorities, local authorities and chief constables until 2 July to submit objections.
Following the announcement, North Wales Police Authority accused the UK Government of waging a "cynical misinformation" campaign over the merger plans.
Ian Roberts, chair of the authority, said: "We are extremely disappointed that Charles Clarke has decided to ignore the wishes of the people of north Wales.
"They have still failed to answer fundamentally important questions about many crucial issues including funding and accountability.
However, Geraint Price Thomas, chairman of Gwent Police Authority and spokesman for Police Authorities Wales, who has previously voiced opposition to the merger, said he now accepted it would happen eventually.
"We're realistic, we have to accept that Charles Clarke has the ability to deliver this, and at the end of the day what is important is a better and effective police service for the Welsh people".
But he said the merger process to date had been "flawed".
"We believe that we do now have to get in there and explain to the Home Office the practicalities as to what is actually needed to deliver an effective reorganisation."