Patients with mental health problems will be forced to undergo treatment or be returned to hospital by health practitioners.
Controversial new measures in the Mental Health Act called community treatment orders (CTOs) will extend compulsory treatment beyond hospitals and into people's homes.
Paul Farmer of mental health charity MIND was concerned CTOs "risk casting the net too widely and subjecting people to compulsory powers when it is neither necessary nor appropriate."
Rights are crucial and it is necessary to "safeguard them against the misuse of potentially oppressive powers," Mr Farmer added.
MIND is also angry that support for those subjected to CTOs has been delayed for six months by the Department of Health.
The Department of Health has failed to provide guidance over how any service would work or fit into budgets, the group said.