Scottish independence campaigners are backing Nicola Sturgeon's demands for a new referendum
Sir George Mathewson, the former chairman of Royal Bank of Scotland and an honorary vice-president of Yes Scotland, also suggested Nicola Sturgeon may have pulled the trigger on a second independence referendum too soon with Scotland's economy slowing down.
Sir George called on the SNP to move its arguments for independence away from the economy and focus instead on achieving its goal over a longer timescale.
He said: ”I would prefer to see Scotland independent but how we get there, under what situation, is an issue.”
Nicola Sturgeon's independence dreams have suffered a fresh blow
The whole independence issue has got mixed up with Brexit, and I'm not sure I'm in favour of that
Sir George Mathewson
And in comments which will come as a blow to Ms Sturgeon, Sir George said he had sympathy with former SNP deputy leader Jim Sillars, who will refuse to back independence if it means rejoining the EU.
He told the Times: ”I’m not a great lover of the EU. The whole independence issue has got mixed up with Brexit, and I'm not sure I'm in favour of that."
Sir George said Ms Sturgeon had staked her right to hold a second independence referendum by the spring of 2019 on the basis that Scotland voted to remain in the EU.
Sir George Mathewson said an independent Scotland should not join the EU
But he added: "Brexit has to be decided quickly and I think independence will happen over a longer period after that."
He was speaking after former SNP minister Alex Neil called for Scottish independence and EU membership to be "decoupled".
Mr Neil and a number of other SNP MSPs voted for Brexit despite their party's commitment to the EU, after Brussels imposed austerity measures on Greece and Portugal in the wake of the financial crisis.
Scotland is running a higher deficit than either of those countries and would face similar stringent cuts to its public spending to join the EU.
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Sir George suggested Ms Sturgeon may have been better off delaying a referendum until her party could make a better case for running the economy, but added economics was not the most important issue for “Yes" voters.
He said: ”It's true that the economics are different, but I'm not sure that the decision [to vote for independence] is ultimately made on an economic basis; whether it should be is another issue," he said. "We're in a different ball game politically as well as economically. The SNP can argue with a degree of truth that the 2014 referendum was won on the basis of the UK remaining in Europe."
The latest snapshot of the Scottish economy predicts growth will continue to lag behind the wider UK for at least two years.
A report by consultancy PwC said the continuing downturn in the oil and gas sector and an increasing trend of weaker growth in Scotland's financial services were the main drivers behind the downturn.