An angry passerby has captured the moment they've yelled at a Domino's delivery driver for leaving their baby in their car unattended.

The delivery driver left her baby in the car while she delivered the food, and while they were gone, a concerned passerby removed and kept the car keys.

When the delivery driver returned, the angry passerby could be heard saying, “someone could’ve taken your baby!”

“Anybody could’ve got in your car and driven away with your baby!”

The concerned citizen reported the incident to the police, who issued the driver with a warning.

However, Transport Workers Union WA spokesman Tim Dawson said that it was "just horrific" that delivery drivers had to drive with their children in the car in order to make a living.

The Transport Workers Union said that food delivery drivers and riders are vulnerable, with some working for third parties earning just $5.90 an hour.

The woman's employer told 7NEWS that her shift was over and that the woman was doing "one last job before going home" as her partner worked at the same pizza shop and handed over childcare duties.

Domino's is currently investigating the matter "as a priority" and said it supports working parents.