Giving an £86m mental health contract to a firm specialising in physiotherapy could be a "disastrous decision", a campaign group has said.
Bristol, North Somerset and South Gloucestershire Clinical Commissioning Group (CCG) said Vita Health was "the best bidder" for the contract.
However, Shaun Murphy of Save our NHS said the private firm had "no record of providing talking therapies", which was disputed by the CCG.
The company takes over on 1 September.
Speaking at a CCG meeting, Mr Murphy said: "A company which provides physiotherapy is being given a contract to run a key mental health service. It has no record of operating in the Bristol area."
Mr Murphy said it was a "potentially disastrous decision".
The contract is currently provided by 17 different organisations but the CCG has been working since July 2017 to commission a single service to work across the region, the Local Democracy Reporting Service said.
Vicki Palmer, chief executive for Oasis-Talk, one of the existing providers, said in a statement: "This decision is likely to cause chaos and/or depletion in local mental health services and puts at risk the 20,000 people a year who need well-coordinated, clinically effective services to meet the growing mental health needs."
She added that local knowledge and proven clinical expertise were "essential".
Medical director Martin Jones, from the CCG, argued that Vita Health had an "excellent track record of delivering accredited psychological therapies in other parts of the country".
He added the firm is accredited by the Royal College of Psychiatrists and The British Psychological Society, and currently holds the NHS IAPT contract for Basildon and Brentwood CCG, as well as providing talking therapies services on behalf of a number of other NHS organisations.
Vita Health Group CEO Derrick Farrell said the firm wants to make a real difference by "delivering the right mental health care, in the right place and at the right time".