Tory candidates Alexander Burnett and Colin Clark have criticised Brian Souter for donating £1million to the Scottish National Party.
Last week, the transport tycoon vowed to match every donation received by the SNP during the year of the independence referendum – pound for pound.
Mr Burnett, who resides in Banchory, said: “Brian Souter should be spending his money on worthwhile investments – such as his own bus company, Stagecoach.
“Across the region, hardworking people are being forced to rely upon unreliable bus services provided by Stagecoach.
“Maybe Brian Souter should look to investing some of his cash on an improved service.”
Sir Brian recently donated £100,000 to Business for Scotland and to Christians for independence, which are both campaigning for a “Yes” vote
Better Together, which is campaigning for Scotland to remain part of the UK, has previously accused Yes campaigners of running front organisations to get around funding rules.
Yes Scotland has claimed the pro-UK campaign is funded by wealthy landowners and “rich Tories” without a vote.