Research by the Liberal Democrats revealed the number of SQA qualifications gained by offenders has dropped by 21% from 4,789 in 2013-14 to 3,806 in 2015-16.

The party said the figures, obtained using freedom-of-information legislation, demonstrated a need for a "culture shift" in Scottish prisons.

Justice spokesman Liam McArthur said the drop was concerning and called for a review of purposeful activity for prisoners.

He said: "All the evidence shows that gaining valuable qualifications while in prison can transform people's life chances, enabling them to find employment after release and reducing their chances of reoffending.

"Time and again prison inspectors have highlighted the need to boost purposeful activity rates.

"Combined with these statistics, this should lead the Scottish Prison Service (SPS) to review the provision of purposeful activity in our prisons.

"We need to get to the bottom of why people aren't taking the opportunity, or getting the opportunity, to get on in life.

"The Scottish Government must also ensure that the SPS has the resources it needs to deliver personal development programmes that will ultimately reduce crime, make our communities safer and save money in the future.

"Meaningful reform that focuses on transforming people's life chances and effective rehabilitation is long overdue."

An SPS spokeswoman said: "The SPS delivered over seven million hours of purposeful activity in the last financial year across all prisons.

"We are currently developing a new framework document to set the direction of purposeful activity for the future.

"While the number of those completing SQA qualifications has dropped recently, the number of vocational and employment-related qualifications has risen, as has the average number of purposeful activity hours per week per individual."