Autism and ADHD care is at risk of descending into chaos, NHS bosses are warning, as costs spiral out of control and unregulated private providers capitalise on the huge demand for help.

The NHS Alliance, which represents health managers, says the current system represents a “bad deal” for patients and taxpayers alike.

It points to big variations in what the NHS is being charged for assessments and care – in one case, a local health board was paying £300 to £3,000 for similar services.

The group says there has been a rapid expansion in new providers – both private firms and charities are involved – and NHS managers are struggling to ensure the quality and safety of care being provided.

The government said an independent review into services would be published soon and it would act on the findings of that, promising a “new national approach” for autism, ADHD and mental health.

Ahead of that, the NHS Alliance has been gathering information from integrated care boards, which hold the budgets for local services, about the current state of care.

Under the right to choose policy, patients can decide to opt for care from both NHS and non-NHS autism and ADHD services.

The initiative is aimed at helping patients bypass the long waiting lists that have developed in recent years.

The NHS Alliance said the policy has led to an influx of new providers, helping to reduce some of the longest waits for adults and children, but at a cost.

It found a number of boards were reporting sharp rises in spending, describing it as “out of control”.

One board saw costs rising 10-fold in a year, to £1.5 million a month.

Another saw annual spend jump from £4 million a year to £30 million over the course of two years.