Members of Parliament have warned of the urgent need to improve the diagnosis times and subsequent treatment of children with autism – after it was revealed that parents of children with suspected autism are having to wait at least 44 months.

The figures have sparked more than 140 MPs into action, who have written a cross-party letter to the health secretary Jeremy Hunt.

The figures, obtained via a freedom of information request, relate to children under the age of five who need a specialist autism assessment after being referred by a GP or other health professional, the Guardian reports.

In the letter, MP Paul Williams, who is also a GP, said: “This is an issue of profound unfairness. While children are waiting and their parents are struggling, they often don’t get much-needed access to support in school, and they fall behind their peers.”

Mark Lever, Chief Executive of the National Autistic Society, added that such “unacceptable” delays could make or break a child.

“An autism diagnosis can be life-changing. It can explain years of feeling different and help unlock crucial advice and support. The longer someone lives without the right support, the higher – and more expensive – their needs can become.”