Entrepreneurs and top executives have made a last ditch appeal to voters to keep Britain in the European Union.
Virgin founder Richard Branson and WPP (WPPGY) CEO Martin Sorrell are among 1,285 business leaders who signed a letter published in The Times on Wednesday. They say their companies -- which together employ more than 1.75 million people -- are stronger in Europe.
A record number of people have registered to vote in Thursday's referendum on whether the U.K. should remain a member of the EU, or become the first country to leave the bloc of 28 nations. Opinion polls suggest the result is too close to call.
The letter's signatories include big shots such as BP (BP) CEO Bob Dudley, Burberry (BBRYF) CEO Christopher Bailey, and Paul Kahn, the president of Airbus Group UK (EADSF), as well as 910 small and medium-sized business owners.
Related: Why you should care about the Brexit vote
Former New York mayor and businessman Michael Bloomberg is also on the list. He helped fund the "remain" campaign.
"Businesses and their employees benefit massively from being able to trade inside the world's largest single market without barriers," the business leaders wrote.
A British exit (Brexit) from the EU is almost certain to mean the U.K. can no longer trade freely with Europe.
The letter comes on the last day of a campaign that has divided the country. Latest opinion polls suggest up to 10% of voters are still undecided, and both campaigns are working flat out to sway the vote their way.
Brexit voters: Why I want to leave the EU
The campaign to leave the EU has also scored some business backers, most notably the vacuum cleaner magnate James Dyson and Anthony Bamford, chairman of construction equipment firm JCB.
"Brexiteers" say the EU places a heavy burden on business through regulations, and that Britain could trade more with the rest of the world if it were outside the bloc. The Vote Leave campaign did not respond to CNNMoney's request for comment on Wednesday's letter.
