Plans to merge the four police forces in Wales have been strongly criticised by a group of MPs.
The government says Welsh forces are currently too small
The Commons Select Committee on Welsh Affairs accused the government of a "one size fits all" approach.
It says the government is rushing ahead to create a single constabulary without considering Wales' geography, politics and culture.
The home secretary argues the existing four Welsh forces are too small to deal with the demands of modern policing.
Charles Clarke has said in particular these demands are fighting terrorism and serious organised crime.
These merger plans are in line with similar changes proposed for police forces in England.
Hywel Francis, the Labour chairman of the Commons Select Committee on Welsh Affairs, accused the government of using Wales as a guinea pig and of not listening to public concerns.
Mr Clarke's plans to merge the four Welsh forces into one have already been strongly criticised by chief constables and police authorities.
Plans for the radical restructuring of the 43 forces in Wales and England were revealed last September when the Inspectorate of Constabulary described police structure as no longer "fit for purpose".
Wales' police chiefs have been told by the home secretary they have until Friday to agree to merge South Wales, Dyfed-Powys, North Wales and Gwent.