NASCAR driver Hailie Deegan has been ordered to undergo 'sensitivity training' after branding an opponent a 'retard' during the live stream of a virtual race.

The 19 year-old made the comment after being hit by another car, but immediately apologised and said there was no excuse for her behaviour.

She wrote on Twitter: "Earlier tonight I used an insensitive word during an online race being broadcast on twitch.  It was inappropriate slang and a stupid thing to do.

"I apologise to everyone who was offended by it. There's no excuse for it, and I know I have to do better for my sponsors and my fans."

Deegan, daughter of motocross legend Brian Deegan, became the first woman to win a race in NASCAR’s K&N Pro Series West in 2018 and currently competes for Ford Racing Development.

Ford signed Deegan to be part of the development program ahead of the 2020 and issued a statement after the incident.

"We are aware of this inappropriate comment," they told NBC Sports. "Hailie immediately acknowledged this mistake, has apologized and promised to be much more thoughtful in the future."