Viral video shows the hilarious moment mother accidentally moons crowd at school sports day

Footage has gone viral after one mother accidentally gave school children "more at sports day than they were expecting" after an unfortunate incident.

A British mother has posted the hilarious moment she mistakenly mooned a crowd of students and teachers at the school's sports day after tripping over during the parents' race.

Katie Hannaford was embarrassed when she flashed people on the sidelines after her eight-year-old daughter begged her to participate.

The video shows Hannaford sprinting across the field when she trips and falls to he knees.

Her dress flew over her head revealing her underwear.

One adult behind Hannaford can be seen covering her mouth in disbelief.

"When the kids got more at sports day than they were expecting! Haha," Hannaford wrote on Facebook. "If you can't laugh at yourself then what's life about ay!

"Sorry kiddos and anyone else watching!" 

The video has been shared online and instantly went viral.

"Ten points for the faceplant and 100 for the sense of humour," one person commented.

"Good job you had knickers on," another wrote.

"This will go down as the most funniest sports day performance ever," a third said.