The Scottish Court Service said all outstanding fines and financial penalties are being pursued. Enforcement actions include benefit deductions, freezing bank accounts, arresting wages and seizing cars.
Commenting on the figures, Conservative justice spokesman David McLetchie said: "These levels of non-payment bring the whole system into disrepute and undermine public confidence in the justice system. We need to examine how we can more effectively collect such fines.
"Fiscal fines are supposed to be an alternative to prosecution, but when they are simply ignored by so many, the public will conclude that they are not much of an alternative."
Lewis Macdonald, Labour's justice spokesman, said: "It is completely unacceptable that one in three people are not bothering to pay a penny towards the fines imposed by our courts and this illustrates a major weakness in our justice system.
"The SNP Government has to address a situation where one of our courts' most common disposals has become unenforceable. Much of the £6.5 million in fine arrears is money lost to the public purse at a time when budgets are being squeezed."
