Sir Brian Souter was the biggest individual donor to any political party after he gave £1 million to the SNP in the last quarter.
Only Highstone Group Ltd gave more money to any party than the Perth-based bus tycoon, with Ukip benefiting from their £1.08m gift.
Overall, Sir Brian’s money represented the vast majority of the £1.1m given to the SNP.
The Stagecoach chairman recently donated £100,000 to Business for Scotland and to Christians for independence, which are both campaigning for a Yes vote in next month’s referendum.
A spokesman for the SNP said: “The referendum is Scotland’s one opportunity, and it’s a fantastic sign of confidence that Brian and others the length and breadth of Scotland are stepping up to the plate to do what they can so that we have the resources to take on the Westminster establishment and win that vital Yes vote.”
Overall, the Conservative Party moved further ahead of Labour in raising funds to fight the 2015 general election, raking in £7.2m in the second quarter of the year.
That was almost double the opposition’s total, although there was a near threefold leap in the cash handed to Ukip, which raised £1.4m in the period around its success in May’s European elections.
That put it ahead of the Liberal Democrats on £1.2m.
Labour said the figures showed another £2m had been raised by the Tories from donors who attended private dinners with David Cameron and other senior ministers, taking the total to £5m this year.