Almost half of children awaiting an autism assessment have been doing so for more than a year – with hundreds more waiting upwards of four years, figures show.

Data obtained by the Scottish Conservatives using freedom of information legislation shows that of the 12,500 children referred for an autism spectrum disorder (ASD) assessment and still awaiting one, 5,700 have been waiting more than 12 months.

One in five children – 2,180 – have waited more than two years, while 240 have waited more than four years, according to the figures.

Four of Scotland’s 14 NHS boards said they did not have the figures on assessment waiting times, meaning the true figure cannot be fully understood.

Conservative MSP Graham Simpson accused Health Secretary Humza Yousaf of “letting down” children and their families, and he urged the minister to act urgently to help children in need of support.

The Central Scotland MSP said: “For families with children waiting to get assessed, these shocking figures will strike a depressingly familiar chord.

“These delays are unacceptable. Having to wait a year for diagnosis and support to be put in place could be seriously detrimental to a child with autism – but having to wait more than four doesn’t bear thinking about.

“It will undoubtably also have an impact on parents, who may be struggling to cope with the unique challenges of raising a child with autism without any extra help.

“Sadly these huge delays for assessments are symptomatic of a wider waiting times crisis in Scotland’s NHS that has developed on the SNP’s watch.

“Poor workforce planning by successive SNP health secretaries has led to a shortfall in frontline medical staff across our NHS.

“Humza Yousaf is currently letting down children and their families, so he must act immediately to help bring these awful waiting times down.”

A Scottish Government spokesperson said: “The Scottish Government is committed to supporting children and young people with neurodevelopmental profiles of need, including those with autism spectrum disorder. More than £3 million was allocated in 2021/22 to help NHS boards build professional capacity and support children and young people with neurodevelopmental support needs.

“As outlined in the national neurodevelopmental specification published in September 2021, we expect that children and families receive the support and access to services that meet their needs at the earliest opportunity, regardless of diagnosis. For many children and young people, such support is likely to be community based, and should be quickly and easily accessible.

“Separately, we have established the national autism implementation team, in partnership with Queen Margaret University, to support the redesign of autism diagnostic services. The team is working with NHS boards to examine diagnostic pathways for autism and establish regional experts.”