Figures show that the previous waiting time of four weeks, maintained from 2012-13 to 2016-17, jumped to 13 weeks last financial year.
That leap from one month to three was revealed by the Scottish Government in response to a written question from Lothian MSP Miles Briggs, and it has prompted fellow Conservative Rachael Hamilton to demand an explanation.
Ettrick, Roxburgh and Berwickshire MSP Mrs Hamilton said: “With social media and other modern-day pressures, there seems to be significant rise in the number of mental health problems in young people, which is very worrying.
“To hear that they are now having to wait for three months to see someone in the Borders is just not acceptable.
“I will write to the minister for mental health for an explanation to why there has been such a significant jump in so little time”
NHS Borders chief officer Robert McCulloch-Graham said that staffing availability and the overall capacity of the service was responsible for the increase in waiting times, saying: “We have introduced a new IT system which has changed the way that we record and report data and makes reliable comparisons to past performance more difficult.
“Patients referred to our service as a priority continue to be seen either the same working day or within five working days, dependent on the urgency of the referral.
“However, we do recognise that for routine referrals there appears to have been an increase in the average time from referral to treatment for patients accessing this service.
“This has been due to a combination of staffing availability and overall capacity within the service.”
“To improve the situation, we have increased the capacity of the team and have already seen a reduction in waiting times.
“We expect our waiting times to return to previous performance levels in the next six months.
“We continue to work closely with social care colleagues to provide a diverse and rounded service for young people in the Borders.
“For example, young people who do not require specialist mental health interventions can access other resources such as the Quarriers service recently commissioned by Scottish Borders Council.”