Mum demands justice after her son, 15, was left needing surgery after alleged assault by several adults at a junior footy carnival

An Australian mum is demanding justice after her 15-year-old son was allegedly assaulted by several adults at a junior footy carnival in an attack that left him needing surgery.

Police are investigating the incident that left Blake Cubby-Francisco with a broken collarbone following an alleged assault at Rowden Park in St George, Queensland on June 27.

The teenager's mother, Kylie Francisco, claimed her son was watching his nephew compete in a junior rugby league carnival when he saw his relative get hurt.

She said Blake went to the side of the field, where his nephew's coach abused him.

Ms Francisco said her son said something back and a man followed Blake as he moved away.

She explained that her son can't remember if he was grabbed or tripped, but she said witnesses claim to have seen four men on top of her son behind an ice cream truck parked nearby. 

Blake's collarbone was broken during the alleged scuffle and his face was battered.

Ms Francisco has been left appalled that her son - who will have surgery on his collarbone on Monday - was allegedly assaulted by adults.

'This could have been prevented,' Ms Francisco told News Corp.

'Now my son has to have surgery on Monday … he has to have a plate put in his shoulder.'

Police have confirmed that they are still looking into the incident and have not laid any charges.