Opposition politicians have demanded Culture Secretary Fiona Hyslop is dragged before a Holyrood committee to explain why she gave £150,000 of public money to T in the Park.
In a joint statement, Scottish Conservative, Labour and Liberal Democrat MSPs called for the SNP minister to answer questions on the controversy.
It comes after First Minister Nicola Sturgeon ruled Ms Hyslop had acted appropriately in awarding the grant to the multi-million pound Perthshire festival.
In a letter to Education Committee convener Stewart Maxwell, fellow members John Pentland, Liam McArthur, Mark Griffin and Liz Smith said: “In parliament last week, Fiona Hyslop declared that the award of £150,000 to the T in the park festival earlier this summer was given to ‘ensure its viability’.
“Her comments have only served to deepen the growing confusion over why the award of state aid was granted to this event. The money was released after the event took place. T in the Park is run by a profitable company.
“There has been no adequate explanation as to what the money was used for; consequently we believe the business case for the award drawn up by civil servants should be published.”
Former Scottish Government advisor, Jennifer Dempsie, set up a meeting between festival bosses DF Concerts and ministers to discuss funding, although she did not attend.
After a meeting with ministers on May 28, the culture secretary signed off an “ad hoc state aid” package for the festival on July 2.
Ms Hyslop has insisted it was required to help ensure the festival took place, although it has been reported that Ms Hyslop did not take legal advice from Scottish Government lawyers before making the award. It is not known whether civil servants drew up a business case for the Minister.
A Scottish Government spokeswoman said: “After looking into the matter carefully and taking advice from the Permanent Secretary, the First Minister has concluded that the Cabinet Secretary for Culture acted entirely appropriately in her handling of this issue.
“The awarding of this funding was based solely on the merits of the case following an objective assessment by Scottish Government officials.”