The growing problem of children waiting for psychiatric services in Wales is being ignored by ministers, it has been claimed.
The number waiting more than 14 weeks has soared in the past year.
Ongoing problems with mental health services in Wales were previously highlighted in a report last year.
The Welsh government said cutting waiting times was a priority, and extra funding of £250,000 had been announced recently.
Welsh Lib Dem leader Kirsty Williams said: "Sadly the Welsh Labour government is determined to bury its head in the sand and ignore the catalogue of concerns and warnings that young people in Wales are being put at risk.
"This complacency is astounding and the Welsh Labour government should hang its head in shame."
The number of children in Wales waiting more than 14 weeks for psychiatric services rose from 199 to 736 in the 12 months up to January 2014.
Problems with the child and adolescent mental health service (CAMHS) were raised in a report last December despite some progress being recognised since a previous study in 2009.
The joint review by Health Inspectorate Wales and the Wales Audit Office said children were being put at risk because of inappropriate admissions to adult mental health wards.
The assembly's children's committee is currently holding an inquiry into the service.
In its evidence to the committee, the Royal College of Psychiatrists in Wales said there was "significant variation in access" around Wales.
A Welsh government spokesperson said: "Waiting times are a priority in our CAMHS improvement plan.
"We have seen an increase in demand in recent years in part because of changes in 2012 for services to care for young people until their 18th birthday.
"The Mental Health (Wales) Measure, which came into force in 2012, enables more patients be seen by local mental health services, which means that CAMHS can concentrate on treating the most complex patients.
"The health minister [Mark Drakeford] recently announced an extra £250,000 a year for CAMHS services, which will ensure more young people are cared for in Wales, reducing the need for costly out-of-area placements."