The doctor tasked with chairing a Labour study into NHS staffing says the issue is ''undoubtedly'' one of the biggest challenges the health service is facing.
Number Of Youngsters Waiting For Mental-Health Help Trebles
The number of children and young people waiting more than a year for specialist help with mental-health problems has almost trebled, according to new figures.
Of those starting treatment in the period April and June 2016, 147 had been on a waiting list for more than 12 months, up from 52 in the previous quarter.
The Scottish Government has set the target of people waiting a maximum of 18 weeks for treatment after being referred to specialist Child and Adolescent Mental Health Services (CAMHS).
Of the 4,642 children and young people who began treatment in April to June, 77.6% were seen within the target time, down from 84.4% in the first three months of 2016, according to NHS figures.
Liberal Democrats said the statistics showed a "crisis'' in CAMHS and that it is time the Scottish Government "got to grips with the challenges'' the sector is facing.
Separate statistics showed more adults with mental-health problems are also waiting longer for psychological therapies.
There were 12,779 patients who started such treatment in April to June, with 81.2% of them having been seen within 18 weeks.
That is down slightly from 82.8% from the first quarter of 2016 and shows the target of having 90% of people starting to receive help within 18 weeks has not been met.
In NHS Forth Valley just over half (53.9%) of patients starting their treatment did so within the target time while in NHS Grampian the target was met for two-thirds (66.3%) of people.
Meanwhile, only 28% of children and young people in NHS Forth Valley began their treatment within 18 weeks, the latest figures showed, the lowest of any mainland health board, while in NHS Shetland the proportion was 22.7%.
Across Scotland, the figures for CAMHS show a slight improvement from 12 months ago, with 76.7% of those who began treatment in April to June 2015 being seen within the target time.
Mental health minister Maureen Watt said: "The continued and substantial increase in demand for child and adolescent mental health services clearly show that in the past there were far too many children who were unseen and whose need was unmet for far too long.
"To respond to this, we have doubled the number of psychologists working in CAMHS.
"We are also investing an additional £150 million over five years and will be publishing a new mental-health strategy at the end of the year.
"I have been clear with boards that any falls in performance towards the challenging 90% target, or children experiencing long waits, is simply not good enough.''
Lib Dem health spokesman Alex Cole-Hamilton said: "The First Minister was right to appoint a dedicated minister for mental health after the election.
"It is time that Maureen Watt got to grips with the challenges facing CAMHS and delivered the support that mental-health professionals and patients need.
"We need a step change in the way that we treat mental ill-health in Scotland.
"That means more investment, specialist CAMHS beds north of Dundee and urgent steps to finish Scotland's long overdue mental-health strategy.''
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