Bankier is one of more than 120 bosses of Scottish businesses who have signed the letter in a personal capacity.
He told OLN: “We’ve a business that operates on both sides of the border – in fact, two- thirds of it is in England and only the smallest part is in Scotland.
“I’ve no particular big passion to do business in two countries with different tax regimes and possibly different currencies.
“Independence is a lovely concept, good for the heart and makes you proud to be Scottish, but the reality from a business point of view is that it doesn’t pass the test.”
Bankier has built the Whisky Shop to a UK-wide chain of 23 shops and recently revealed plans to expand at home and overseas.
He was joined on the list of the open letter’s signatories by several Scotch whisky distillery bosses and other drinks industry leaders.
They include: Robert Anderson, chief executive of Tomatin; Ian Curle, chief executive of Famous Grouse producer Edrington; James Espey, owner of Last Drop Distillers; Keith Falconer, chairman of Adelphi Distillery; William Grant director Peter Gordon; Leonard Russell, managing director of Ian Macleod Distillers; Drew McKenzie Smith, managing director of Lindores Distillery; Graham Stevenson, managing director of Inver House Distillers; former Scottish & Newcastle chairman Sir Brian Stewart; and Fraser Thornton, managing director of Burn Stewart.
The letter states that “the business case for independence has not been made”.
It adds: “Uncertainty surrounds a number of vital issues including currency, regulation, tax, pensions, EU membership and support for our exports around the world.”
Former Scotch Whisky Association chief executive Gavin Hewitt is also a signatory and was involved in recruiting others. He said 11 Scotch whisky firms were among more than 100 who declined involvement through fear of “a backlash”.
He told OLN: “Everyone I approached on the whisky side of business was opposed to independence but fewer than 50% of those were willing to sign up for fear of the consequences of expressing opposition to independence with the current or a future SNP government.”
He added there was fear of a “backlash on planning or grant applications or because they were involved in delicate discussions with the Scottish government which they did not want to jeopardise”.
Chivas Brothers owner Pernod Ricard said it had no contingency plans in case of a yes vote.
Chivas chief executive Laurent Lacassagne said: “We are currently enjoying a very favourable environment which includes currency stability, membership of the EU and trade agreements under the World Trade Organisation. We are concerned by every kind of change which could impact negatively on this favourable environment.”
Pernod Ricard UK managing director Denis O’Flynn said different tax rates, currencies and administrations could lead to “a level of complexity that doesn’t need to be there”. He added: “Things as they stand, from a commercial point of view, are much easier to manage.”
The referendum on independence in Scotland takes place on September 18.