With less than a month until the European Union referendum, Britain's position within the 28-country bloc remains uncertain. Businesses and politicians have thrown their weight behind one of the two campaigns, while depending on which polls one believes, either 'Remain' and 'Leave' are neck or neck or the former is heading for a landslide win.

Supporters of the Leave campaign have argued Britain would thrive financially if no longer subject to the EU's red tape, while a number of economic think tanks and international bodies have warned UK business could suffer outside the EU, and that foreign companies would be less eager to do business in the UK post-Brexit.

A number of world leaders, including President Barack Obama, have also issued stern warnings over a potential Brexit. Last month, Obama said the UK would be at the "back of the queue" for any trade deal with the US if the country broke ties with the EU.

IBTimes UK spoke to the leaders of two transatlantic businesses to find out how a Brexit could impact trading on both sides of the Atlantic and in the eurozone. John-Paul Savant, the CEO of ATG Media, one of Europe's leading online auction networks, admitted Obama's comments were concerning for businesses with close ties to the UK.

"This [the prospect highlighted by Obama] is a concern not only for our business, but many multinationals and UK-based city firms who feel an exit would have a widespread ripple effect on how they do business with the USA," he said.

"You need only look at the warnings from the Bank of England and UK Trade and Investment to get an idea of how hard it would be to renegotiate trade deals. The government has stated it would take another eight to 10 years to achieve a renegotiation of all its deals with the EU alone. Such a time frame would, I believe, damage our business."

Toby Southgate, the worldwide CEO of Brand Union, one of WPP's global branding agencies, echoed Savant's words but warned predictions could well be proved wrong.

"The honest answer is no one knows," Southgate said. "Britain has been part of the EU since its inception. People can and do have opinions on the consequences of the final decision, but no single outcome can be definitive or predictable."

Savant and Southgate both have strong ties with the UK and the US, given the former was born in San Francisco but lives in London, while the latter has followed the opposite route.

However, while both agree the US administration is firmly in favour of Britain remaining in the EU, Southgate suggested the UK referendum is far from the minds of most US companies at a time when American voters are focused on the upcoming presidential elections.

"For some businesses, my own included and anyone doing business internationally, there's certainly interest in both the referendum and its implications on trade, the financial markets – particularly currency," he said.

"But that interest pales into insignificance against the backdrop of 'Donald Trump vs Hillary Clinton and their likely race for the White House."