JCB chairman Lord Bamford has written to his company's 6,500 employees in the UK to explain why he favours a vote to leave the European Union.
In the letter he said he was "very confident that we can stand on our own two feet".
He also said that more than 53% of all UK exports go to non-EU nations.
In response, the Remain side said firms including Airbus and BMW, had already written to their staff to put the benefits of staying in the EU.
A referendum on whether the UK should stay in the EU will be held on 23 June.
Lord Bamford told his employees that the referendum's outcome "will determine the future of our country" with a "lasting impact on the lives of our children and grandchildren".
His letter states: "I voted to stay in the Common Market in 1975. I did not vote for a political union, I did not expect us to hand over sovereignty to the EU.
"I certainly did not expect unaccountable leaders in Brussels to govern over us.
"So do I wish to remain in an EU of diminishing economic importance as it moves towards ever closer union? Or do I want us to pull out of the EU, reclaim our sovereignty and regain control of how we trade with Europe and the world?"
The JCB chairman told workers it was up to them to make a choice, but urged them to vote in the referendum.
A number of firms have written to their UK staff to put the case for staying in the EU, including BMW, who emailed a message saying the decision was ultimately a matter for the British public, but highlighted the "significant benefit" the company said it derived from the free movement of people within the EU.