A porn studio fired a longtime producer after its star actress, Nikki Benz, accused him of stomping on her head and choking her out during a shoot ... but the guy's calling BS.

Brazzers -- a porn production company -- tells TMZ ... they've officially cut ties with Tony T., who allegedly went too far during a recent sex scene he directed with Nikki.

Nikki claims Tony choked her and stomped on her head in a fit of rage. It's unclear what allegedly set Tony off, but Nikki claims he attacked her during one of her sex scenes. It appears her claim is that she did something on camera he didn't like.

Apparently, the sex scene was completed but Brazzers tells us it will not release it, saying the video "stands in direct contrast with our mandate to ensure that performers' consent, boundaries and limits are respected."

As for Tony, his rep tells us he denies the allegations and laments the actions taken by Brazzers. We're told he's confident his name will be cleared.

JENNA JAMESON BACKING NIKKI
TMZ.com