Hours before the polls open, Sir James Dyson has renewed his support for a Brexit, saying remaining in the EU would be an "act of self-harm".
"As the world's fifth-biggest economy we can decide for ourselves crucial policies that will affect all our lives, or we can cede control to an undemocratic and opaque EU," he wrote.
"To think Brussels can reform is arrogant and delusional. It is pure fantasy.
"I have been manufacturing and exporting globally for 46 years and have 'sat at the table' dealing with European bodies for at least 25 of those. I can confirm that we have no influence whatsoever in the shaping of Europe's protectionist laws and regulations. Believe me, we've tried."
Dyson decision to ramp up support for the Leave campaign came as Gerald Mason, the senior vice president of Tate & Lyle, wrote to his 800 employees to voice support for leaving the European Union.
In his letter, Mason said EU restrictions had pushed up raw material costs by nearly €40m (£31m) alone, which he said had turned "what should have been a good profit that we would all share into a €25m loss.
"We pay as much as €3.5m of import tariffs to the EU on some of the boats of cane sugar that unload at our refinery, only for the EU to then send that money to subsidise our beet sugar producing competitors in Europe," he added.