The singer-songwriter said she would no longer play gigs with Alex Salmond, the First Minister, because she is fed up with the "playground politics" at Holyrood.
The row began after it emerged the SNP spent 10,000 providing her and her band with hotels, flights and meals.
Labour accused the SNP of paying Thom "kick-backs" for helping its 2007 election campaign and demanded to know who authorised the payments. Thom, 27, from Macduff, Aberdeenshire, featured on a campaign leaflet and is a staunch SNP supporter. She recently performed a duet of Caledonia with Salmond..
In the wake of the revelations, the singer said she waived her performance fees for the events and added: "All I see within the parliament is just playground politics, people trying to make the other one look like an idiot… That is just people being petty. It is something I don't want any part of any more. I won't do any more gigs for the government."