Tony Abbott falls fighting Sydney bushfire

Former Prime Minister Tony Abbott has joined fire crews tackling a bushfire in north Sydney.

Former prime minister Tony Abbott has joined fire crews tackling a bushfire in north Sydney. (AAP)

Tony Abbott has taken a tumble as he stepped out of a fire truck to help battle a bushfire in Sydney's north.

The former prime minister and volunteer fire fighter joined crews at Castle Cove where the blaze broke out on Saturday morning.

NSW Rural Fire Service said the fire is burning behind properties but no homes are currently under direct threat.

Residents are being advised to monitor the situation and take advice from firefighters on the ground.