Fourteen charities which provide services in Cornwall will have funding stopped in July affecting hundreds of vulnerable adults across the county.
Some of the providers affected include Cornwall Stroke Support, Headway Cornwall and the Red Cross Home from Hospital Service.
Cornwall Council said the groups had been given short-term funding and the cuts were being made after judgements about their performance.
The authority said contracts were awarded to 18 organisations in July 2013 to deliver community support, and information and advice services.
It said required standards had not been met in the case of 14 providers and so the contracts were being ended.
Brain injury charity Headway Cornwall said staff had been left "truly devastated" and it was facing closure after it found out the council was to scrap its funding at the end of July.
It said about 95% of its funds come via the council contract.
Deborah Fisher, senior health and social care manager for the Red Cross in Cornwall, said hundreds of people "benefitted each year from the support our fantastic staff and volunteers".
She said: "Whilst we understand the budget constraints facing the council and the difficult decisions it has to make, we are concerned about the impact on the vulnerable adults who use our service."
The council said all the providers had been invited to attend a meeting in April prior to the decision being made.
It said: "It was made clear at this meeting that termination was one of the options being considered.
"We are aware that not all providers attended this session, and detailed information was sent to any who did not attend."
Debbie Pritchard, chief executive of Healthwatch Cornwall, has raised concerns that the decision is "contrary to the council’s health and wellbeing board’s approach to provide community services that keep people well and in their own homes."
She said: “We are very keen to hear from anyone affected by the potential loss of support so we can consider escalating this matter to the health and wellbeing overview and scrutiny committee or raising it at the health and wellbeing board.
“The loss of these services may not only affect the people who use them directly but also those who look after them, and their families.”