The SNP has been accused of changing party policy in return for cash.
Labour MSP Drew Smith made the claim as the Electoral Commission revealed the Nationalists spent £1,141,662 in the Scottish election campaign this year.
The SNP spent almost as much money as their three main rivals combined in the run-up to their historic victory in May.
In contrast, Labour spent £816,889, the Conservatives £273,462 and the Lib Dems £176,300 a total of £1,266,651.
The SNP therefore spent an average of £16,545 for each of the 69 seats they won in the election.
Labour’s 37 seats came at a cost of £22,078 each, the Conservatives spent £18,230 for each of their 15 seats and the Lib Dems’ five seats cost £35,260 each.
In addition the Greens spent £132,464, meaning the two list seats they won in the election are the most expensive in the parliament coming at a cost of £66,232 each.
But Mr Smith said the SNP, who have received a number of large donations from high-profile benefactors recently, were ”reliant” on the cash. He cited a reluctance to pursue bus regulation after donations from Perth transport tycoon Sir Brian Souter.
Mr Smith said: ”The SNP are addicted to big money and reliant on a few large donations from some very wealthy individuals in return for which they are willing to change their policies like on bus regulation.
”No wonder they want to avoid the Electoral Commission rules on spending limits when it comes to the independence referendum.”
But SNP business convener Derek MacKay MSP said: ”Winning elections takes more than money. These figures reveal that we spent less than four years ago and achieved our historic win spending less than our main opponents in getting MSPs elected.”
Figures for the 2007 election showed the SNP spent £1,183,462 while Labour spent £1,102,866. However, the decrease in spending will be partially explained by changes in the way the figures are calculated.
The commission said 22 parties spent a total of about £2.6 million in the regulated period between January 6 and polling day on May 5.
The latest figures cover the three parties that spent more than £250,000. Smaller figures were published in September.
Andy O’Neill, head of the Electoral Commission’s Scotland office, said: ”The information we have published completes the picture on campaign spending at the Scottish Parliament elections.”