The campaign to keep the UK within the EU has been given a double dose of support today (20 May) after two influential business bodies backed Britain's membership of the 28-member bloc.
Simon Walker, the head of the Institute of Directors (IoD), told IBTimes UK that a so called "Brexit" would be "disastrous".
But the director-general said he felt certain that David Cameron would be able to secure "sufficient concessions" from Brussels ahead of the EU membership referendum.
"We are in favour of staying in a reformed EU, there's no doubt about that. We are perhaps a little less certain than the Confederation of British Industry (CBI) that we want to do it come what may. Britain should be the leading force for deregulation inside the EU," Walker said.
Walker's stance is in line with his members since a survey from the business body in 2014 showed that a majority (60%) wanted Britain to stay within the EU so long as Brussels made reforms to areas like employment law and energy policy.
The study, analysing over 1,400 directors, also found that 31% of the respondents would vote to remain within the 28-member bloc in all circumstances.
The research comes ahead of a speech by CBI president, Sir Mike Rake, who plans to urge businesses to "speak out early" in favour of the UK remaining inside the EU.
"No one has yet set out a credible alternative future to EU membership. The current alternatives are not realistic options - little or no influence and the obligation to comply with EU principles whilst still paying most of the costs," he will say.
"Reform will not happen overnight, but by working with our allies on an ambitious, yet achievable, agenda, we can make it a reality."
But the "Out" campaign was bolstered early this week after the chairman of manufacturing giant JCB backed a "Brexit".
Lord Bamford, whose family have donated millions to the Conservatives, said businesses should not fear leaving the EU because the UK has one of the strongest economies in the world.
"We are the fifth or sixth largest economy in the world. We could exist on our own - peacefully and sensibly," the peer told the BBC.
Meanwhile, Tory MEP Daniel Hannan told IBTimes UK that the British public would listen to "successful manufactures" like JCB and Dyson on the issue rather than "disgraced banks".
The Eurosceptic's remarks followed the news that Deutsche Bank, one of the largest lenders in Europe, has launched a probe into whether to move its operations out of the UK in the event of a "Brexit".
The all-Conservative government is expected to publish its EU referendum bill a day after the Queen's Speech on 28 May.
The draft legislation will be the first substantial step from Cameron's party to fulfil its pre-election promise of a vote on the UK's membership of the EU by the end of 2017.