Surrey County Council paid about £2.5m last year to healthcare providers for beds it did not use, it has emerged.
The authority said it was "worried" by the figure paid to health firms Anchor and Care UK but was working to renegotiate the contracts.
Under the terms of the contracts, the council pays the companies for the use of 1,000 beds. Last year, about 10% of those beds were not needed.
Opposition councillors accused the authority of wasting taxpayers' money.
Councillor Eber Kington discovered the figure when he put a Freedom of Information request to the Conservative-controlled council.
Mr Kington, from the residents association group, said: "Anyone in Surrey struggling to care for relatives who may have been told there isn't the money for them to get a bed will be appalled by this."
The council said the contracts were negotiated when there was more demand for beds but now people were opting to stay in their own homes for longer.
Councillor Michael Gosling, the cabinet member for adult social care, said he understood people's anger at the situation but was not being complacent.
He said: "We have ongoing negotiations with the two care home operators to reconfigure the contracts to try and bring the situation into line."