The sale of six residential care homes has been approved by Nottinghamshire County Council.
The Conservative-run council is selling the homes for £1.9m to private firm Runwood which will continue to run them.
More than 2,500 people have signed a petition opposing the sale.
The decision was formally approved at a full council meeting on Thursday. Runwood said it would improve facilities and increase bed numbers.
The sale has been criticised by Broxtowe Tory MP Anna Soubry, who said the price fetched was far below what the six houses were worth.
Andy Belfield, from the Unison union, said: "This is simply a bad deal for residents, taxpayers and staff.
"In July the council told Unison it wants £63m of savings by March 2016, calling into question the financial soundness of this deal.
"The government must intervene over this decision."
County council leader Kay Cutts has said the money raised from the sale of the homes will be reinvested into care for older people
The sale is due to be completed in January 2012.
The homes being sold are Bramwell Care Home, Bramcote; Braywood Gardens Care Home, Carlton; Jubilee Court Care Home, Sutton-in-Ashfield; Leawood Manor Residential Home, West Bridgford; Maun View, Mansfield; and Westwood, Worksop.
Runwood Homes runs 47 care facilities and employs 2,000 staff in the UK.