Wrightbus co-founder William Wright and Ulster-raised pub boss Tim Martin are just two out of 250 business leaders who have signed up as backers of a pro-Brexit campaign ahead of the European Union referendum.
The pair are on a list of 250 business bosses who are backing the Vote Leave campaign.
Last month the Belfast Telegraph revealed Tim Martin - the outspoken chairman of JD Wetherspoon - said leaving the union would restore "democracy" to decision-making in the UK.
The Campbell College past pupil also told the Belfast Telegraph he had not ruled out campaigning for a Brexit.
"I have to put all my ducks in a row before I join any campaign, but 15 years ago I campaigned against Britain joining the euro, and that turned out to be a good decision," Mr Martin said.
And earlier this year Wrightbus founder William Wright came out in favour of the UK leaving the EU.
The business figures, including former HSBC chief executive Michael Geoghegan, hotelier Sir Rocco Forte and Luke Johnson - chairman of continental-style cafe chain Patisserie Valerie - have given their support to Vote Leave in a personal capacity.
The campaign group also announced that former British Chambers of Commerce director general John Longworth, who quit after indicating his support for Brexit at the business organisation's annual conference earlier this month, will take up a new role with Vote Leave.
Mr Longworth, who has been appointed chairman of Vote Leave's business council, said: "This is the most important political debate of a generation. Business is divided on the issue and it is vital the full breadth of business opinion is heard. Many firms struggle with relentless interference from the EU and rules that are stacked in the favour of a select number of businesses.
"If we Vote Leave, liberated from the shackles of EU membership, jobs will be safer, Britain will be able to spend our money on our priorities and we can look forward to faster growth and greater prosperity in the future."
Vote Leave's chief executive Matthew Elliott said: 'We're delighted that John Longworth has agreed to chair Vote Leave's Business Council. His strong business track record and his courageous decision to share his true beliefs with voters makes him an extremely powerful voice in the EU debate."
A survey of small and medium-sized firms commissioned by the group found that 32% said the EU hinders businesses like theirs, while 25% said it helped them, 40% said it made no difference.
The YouGov study indicated that 14% of the firms believed that the EU makes it easier for their business to employ people while 31% said Brussels' rules made it harder for them to employ people, 48% said EU rules made no difference.
Mr Elliott said: "With our growing list of business supporters, Vote Leave will make that case that whilst the EU might be good for big multinationals, for smaller businesses it acts as a job destruction regulatory machine. Brussels hinders smaller businesses, particularly those firms who can't afford to lobby Brussels to curry favour. Jobs, wages and our economy will thrive when we take back control and vote Leave."
Remain campaigners insisted that British business supported a vote to stay in the EU in the June 23 referendum.