Thousands of patients with suspected autism in the Surrey heartlands are waiting for a diagnosis this year, new figures show.

It comes as waiting lists have expanded across England, with an autism charity warning the "diagnosis wait crisis" is taking a toll on patients' mental health, and called on the Government to "urgently fix this broken system".

NHS England figures show there were 204,876 patients with an open referral for suspected autism across the country in September, a 27% rise from 161,827 the year before.

Meanwhile, in the NHS Surrey Heartlands Integrated Care Board area, 4,210 patients were waiting for an autism assessment, down from 4,320 last year.

Of these, 95% (3,990) had a referral that had been open at least 13 weeks.

The NHS target is for every patient with a referral to receive a first appointment within 13 weeks.

Tim Nicholls, assistant director of policy, research and strategy at the National Autistic Society, said the figures should be "a huge wake-up call to the Government to urgently fix this broken system which lets down autistic people and their families".

"An autism assessment can be the first step to really understanding people’s needs and too often people can’t get support without a diagnosis, even though this shouldn’t be the case," he added.

"Waiting for months or years for an assessment leaves people struggling without the right support, increasingly stressed and anxious. It pushes some people to a mental health crisis."

He added without public investment the crisis would persist, "leaving autistic people, families and NHS services under the strain".

Just 1% of the patients with an open referral for more than 13 weeks entering September in the Surrey heartlands received a first appointment that month.

The median waiting time for a first appointment across England is 43 weeks.

An NHS England spokesperson said: "While there remains high demand for autism assessments, we are seeing an improvement in the number of assessments completed.

"But we know there is more to do, which is why we have published new national guidance to help local partners to deliver high-quality autism assessment services and to manage the 161% increase in referrals over the last four years, while providing enhanced autism training for psychiatrists."