A JCB spokesperson confirmed that the company had ended its membership of the CBI, but did not give reasons why.
Sky news had earlier reported that it was due to the group's response to the referendum outcome
JCB's chairman, Lord Bamford, was a prominent supporter of the Brexit campaign.
During the campaign he said: "The UK is the world's fifth largest trading nation. We therefore have little to fear from leaving the EU."
He also wrote to his 6,500 UK employees to explain why he favoured a vote to leave the European Union, saying he was "very confident that we can stand on our own two feet".
The CBI, on the other hand, warned that a UK exit from the EU would cause a "serious economic shock", potentially costing the country Â£100bn and nearly one million jobs.
A CBI spokesman said: "It's always a shame to see any member leave the CBI, but we recognise that businesses have competing priorities and we respect that."
A spokesperson for JCB said only: "I can confirm that JCB is ending its membership of the CBI."
The Sky report said that the Staffordshire-based company had ended the membership in the summer, after the referendum.

It's that time when clubs scramble to strengthen their squads, to find a player who can shoot them to glory or one who can save them from relegation.
Some are flops soon to be forgotten, while others go on to become club legends.
But who has been the best January signing? We are not just talking goals, but their value and contribution to the club.
Take a look at our shortlist below and decide for yourself.
Who do you think is the best January signing? Use the selector below to pick from our shortlist. Once you are done download your image and share with your friends.

The African champions take on the Europeans in Jeju, South Korea, as they look to seal a place in the quarter-finals.
Chambeshi has watched his side play some attractive football in the group stage and is looking for more of the same on Wednesday.
"They have a strong team but we are the African champions, so at least that morale is motivating us a lot," said Chambeshi.
He said his team had fully recovered from the 1-0 defeat they suffered against Costa Rica in their final Group C match.
"We are representing Africa and I think we have the strength and power to match Germany.
They have a strong team but we are the African champions
"We have to respect them, but they have to respect us too."
Zambia's prospects have been boosted by the return of captain Solomon Sakala who sat out the Costa Rica game through suspension.
"I'm happy the captain is back in the team; morale is high and the boys are looking forward to the game."
Chambeshi was part of Zambia's Olympic squad thrashed 4-0 by Germany during the 1988 Games in Seoul.
However, he said revenge was not his main motivation but getting the result to see them through to the next stage.
"In football, there is no revenge; we know everyone is looking at that [Seoul '88 defeat], but we buried that Seoul Olympics defeat.
"We have to do our very best so that we overcome Germany.
"That time Germany had [Jurgen] Klinsmann who was a high-class player.
"We also had good players, but now it's a different scenario."
The construction firm JCB has left the business lobby group, the CBI, reportedly because of its anti-Brexit stance.
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The January transfer window is about to close for another year.
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Zambia coach Beston Chambeshi says his team is highly motivated for Wednesday's Fifa Under-20 World Cup tie against Germany.