County Durham's seven district councils are to be scrapped after the government approved plans for a unitary authority.
The unitary authority will be created in April 2009
The Department of Communities and Local Government decision will mean the loss of about 180 jobs, mostly at management level, according to the county council.
A spokesman called the announcement "a clear decision on the way forward".
But the district councils said moving to a unitary council would be costly and disruptive and have a damaging impact on services.
Chester-le-Street, Derwentside, Easington, Sedgefield, Teesdale, Wear Valley and Durham City had submitted a "Pathfinder to Unitary" bid, which called on several development stages and improvement initiatives leading eventually to unitary status.
But this was rejected in March when the Department of Communities and Local Government said it would only consider the county council's unitary proposal.
Speaking after Wednesday's announcement, Durham County Council leader Albert Nugent, said "It is now time for the district and county councils to move forward together to improve people's lives in County Durham.
"I call upon my district council colleagues to work with us to ensure continuity of service and that the unitary proposal which has been approved realizes its full potential."
In June, a postal referendum organised by the districts showed a 76% were against the unitary plans, with 40% of electors taking part.
Durham District Councils' Forum Chairman, Richard Betton, said: "So much for the prime minister's much paraded promises to 'listen to the people'.
"The amalgamation of the county and district council operations is a massive task and the government timetable is totally unrealistic.
"The district councils need to reflect on the details of the decision and will continue in uninterrupted delivery of quality services that are right for the people we serve."
A county council spokesman said the vast majority of the 22,000 local government workers will be transferred to the unitary authority.
But a single council will mean fewer chief executives, directors of finance and heads of service, he added.
The 375 county and district councillors will be reduced to 126 posts when the unitary authority is created on 1 April 2009.