Footage posted online shows Jamie Jackson, 18, handcuffed and with a wound to his head, being pushed violently to the ground where a police man pins him by pushing his boot into his back.

Jackson can be heard in the footage saying, “I did nothing wrong!”

An investigation has been launched into Jackson’s treatment, as the footage itself does not show the events leading up to his restraint.

Sydney police have launching an internal investigation into the incident at the Gay and Lesbian Mardi Gras.

Mardi Gras organiser Peter Urmson told

“We want a full, open and transparent investigation.”

“Mardi Gras was born out of the problem of police brutality and this shows there is still work to do.”

Photo: YouTube.