Prisoners are enjoying the pay rises as millions of workers are facing wage freezes and job losses.
More than £24.5 million of taxpayers’ cash has been spent on prisoner wages in the last decade.
Last year the average weekly wage paid to prisoners was £9.75 compared to £9.11 in 2006/07.
And the total cost of the scheme was £2.7 million as opposed to £2.5 million three years earlier.
It has been revealed that many were handed cash for simply turning up to rehabilitation classes.
Critics have blasted the prisoner wage increase as an insult to victims of crime.
Tory justice spokesman John Lamont said: “Many ordinary Scots will be rightly asking why, when so many workers have seen their wages frozen or cut, prisoners are bucking the trend and seeing their wages go up.
“Many of these prisoners have been convicted of terrible crimes and to see their wage bill rise so quickly will be galling many of their victims.”
Even if there are no jobs for them to do, prisoners who register to work are currently paid a minimum of £4.80 a week.
A points system is used to determine the scale of pay.
Those who volunteer for placements in the community, such as in charity shops, earn the largest amount at £18 a week.
Catering staff and inmates who enrol on educational courses are paid up to £12.
Laundry workers, cleaners and ground staff get up to £9.
Prisoners also receive a Christmas bonus of between £5 and £10 to treat themselves during the festive period.
Only those who refuse to work or have seriously misbehaved get nothing.
Inmates in open prisons are entitles to an extra £3 a week.
The cash is paid into a special bank account and can be used to purchase items such as cigarettes, stamps and phone cards in prison shops.
Richard Baker, Labour’s justice spokesman said: “This is the kind of soft touch approach to justice that we have become all too familiar with under the SNP.
“The same government that is telling public sector workers to accept a pay freeze is spending £2.7 million on wages for prisoners.
“We know in some cases wages are earned simply from playing board games.
“Kenny MacAskill needs to get a grip.”
John O’Connell, research director of the TaxPayers’ Alliance, added: “It’s crucial that these payments are fair and are in keeping with the economic conditions.
“If taxpayers are struggling through an economic crisis then the prison service has to reflect this in payouts.
“With necessary cuts in public spending coming up, government departments must prioritise to ensure value for money for hard-pressed taxpayers.”
Three days before Christmas more than 200 prisoners were sent home from Scotland’s two open prisons – Castle Huntly in Perthshire and Noranside in Angus.
Those who remained behind bars were treated to Christmas dinners complete with crackers and party hats.
A spokesman for the Scottish Prison Service defended wages paid to prisoners and said so far this year the average handout has fallen by nearly two per cent.
He added: “The payment prisoners receive is dependent on the work, education or training they are involved in.
“Work and improving employability through skills are widely accepted as important elements in tackling re-offending.”