A “No” vote in the marriage equality referendum could have negative consequences for investment in Ireland, three leading Irish American business leaders have told IrishCentral.

None could be identified on the record as they are involved in advising companies considering setting up in Ireland on an ongoing basis.

Two of the three pointed to what happened in Indiana when major corporations such as Walmart forced the governor to step back from legislation widely seen as anti-gay.

All three referred to the outspoken comments of Tim Cook of Apple on anti-gay legislation: “You don't want to be on Tim Cook's radar on the issue under any circumstances,” said one respondent.

Cook recently wrote in the Washington Post that anti-LGBT legislation in some US states is plain wrong, saying the new laws are "very dangerous" and contrary to America's founding principles.

While the parallel is not the same it could well be portrayed in the US media that Ireland is an anti-gay country. Said one, “That could have dire consequences.”

Two of the three pointed to the successful boycott of the New York Patrick's Day parade by Guinness and Heineken that forced a rule change to allow LGBT groups to march as a an example of how corporate clout can change massive events.

All stressed that the reality – that defeat of the referendum would not be a discriminatory move per se – could get lost. "A ‘No’ vote is hardly an indictment of Ireland's sense of fairness. But the issue is moving so quickly, that 2-3 years from now, it could be seen as just that. Tim Cook of Apple is openly gay. Lloyd Blankfein, CEO of Goldman Sachs, became a champion for gay marriage three years ago,” said one respondent.

All three agreed that young American workers and the new generation of business leaders, especially those from Silicon Valley, do not want any taint of anti-gay discrimination in countries they do business in.

“Foreign investment comes down essentially to which cities (more than countries) you want to be in. To send your people to, and to hire and build in. Millennials only want to live in the cities. Modern cities are synonymous with tolerance. You can't apply the standards of a (relatively) conservative and religious country to your only city and expect to be the "best little country in the world to do business in,” said one.

“Inside every global company in Ireland – or thinking about being in Ireland – are plenty of people who don't want the company to be there. Add to that all the competing countries. These decisions come down to finely balanced choices and trade-offs. You'll never know when they choose not to call you.”