Plans for a £26m driverless car test track at the "irreplaceable" Bosworth Battlefield where King Richard III was killed have been approved.
Japanese engineering firm Horiba Mira said the facility near Higham-on-the-Hill would create about 1,000 jobs.
But Dr Phil Stone of the Richard III Society said "Would we build on Passchendaele?" and a protest petition has had nearly 15,000 signatures.
Members of the planning committee voted 12 to 5 in favour of the track.
Councillors had been advised to pass the plan on the second time of asking.
The committee deferred making a decision on the controversial scheme last month in the hope the applicant could rethink some of the design.
Historic England had told Hinckley and Bosworth Council it could cause harm to the significance of the Bosworth Battlefield.
The council said the site was not within a conservation area and would contribute significantly to the economy.
The Battle of Bosworth took place on 22 August 1485, and saw the death of Richard III, whose remains were eventually found beneath a Leicester car park in 2012.
Horiba Mira wants to build an "autonomous vehicle testing track" on 34 hectares (84 acres) of land next to its existing testing centre, which is partly within the battlefield site.
About 25 vehicles, including cars, buses, trucks, military vehicles and construction machinery, could use the facility every day.
But the plans, which planners had recommended councillors approve at a meeting on Tuesday evening, faced substantial opposition.
As well as the criticisms by Historic England, The Battlefield Trust said: "It is one of the most important battlefields in England and its preservation should be of high priority for everyone".
Dr Stone added: "This an almost untouched battlefield, which saw one of the most dramatic episodes in British history. Would you treat Hastings like this? It is irreplaceable.
"People say it is only a small part of the battlefield but this is where Henry Tudor entered and close to where Richard tried to kill him.
"If this area is lost, will it set a precedent? Will it be more next time?"
On Twitter, those opposed to the plans had been calling for support, with @andysargent saying "Hoping Hinckley and Bosworth borough council see sense and deny any development".
Along with the petition, more than 450 letters of objection had been sent to the council.
The site has a heritage centre detailing the battle and sees an annual re-enactment event to mark the anniversary of the battle.
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