Leaders at Wiltshire Council’s Conservative group have said they could challenge the decision at the High Court as they claim the decision was made in private.
The council’s Reform group has also expressed concern about a lack of consultation, with the group’s leader, Ed Rimmer, calling the council “out of touch”.
Mr Thorn said that the council is “committed to supporting residents through these changes and will ask for feedback early in the new year”.
“We will provide clear information including our plans on a new site in the north of the county,” he added.
The Hills Group spokesperson said over the last 11 years costs have increased significantly more than the Consumer Price Index (CPI).
“Recent submissions considered these additional costs along with the cost of essential reinvestment in the sites which would allow us to continue to provide an essential service to the residents of Calne and Purton maintaining the high standards our staff have achieved consistently,” they added.