Jim McColl, who backed a Yes vote in the 2014 independence referendum, was part of an elite group of business figures who attended the private event with Theresa May last week.
Scottish Greens co-convener Patrick Harvie said the Scottish Government should now reconsider his role on their Council of Economic Advisers.
McColl told the Sunday Herald he did not pay to attend the dinner and was invited by a Tory donor he knows.
The event was reportedly held at the home of Sir Jack Harvie, a businessman who has raised millions of pounds for the Conservatives through his Focus on Scotland (FOS) organisation.
McColl said: “I was invited along by a Tory donor and I was intrigued to meet Theresa May and just listen to what she had to say. So I went along and it was a very interesting evening.”
He added: “I and other business leaders are always open to meet any politician irrespective of party and will continue to do so to help influence and achieve the best outcomes for our economy.”
An FOS spokesperson said business people attended its events regardless of their political allegiances.
McColl was one of the most high-profile backers of the Yes campaign in 2014.
But the Monaco resident, chairman of Clyde Blowers, has since cooled on the idea.
Asked in 2015 if he still backed independence, the businessman said: “No, the decision’s been made.”
He added the UK needed much greater transfer of powers to its nations and regions.
McColl said: “I don’t think this is a Scotland-England issue; this is a London and rest of the UK issue. This is all about centralisation.”