A DEADBEAT mum left her baby alone in a car while she shopped for bargains at the Boxing Day sales.

Police said they expect to charge the 27-year-old woman with leaving a child unattended after leaving the 17-month-old boy alone for an hour and a half.

Officers said they were "left aghast" by the incident at Westfield Doncaster shopping complex.

"Investigators have been told that a woman drove to attend the sales at the shopping complex on Doncaster Road with a 17-month-old boy at about 9.30am," Senior Constable Adam West said.

"She parked the car in an undercover car park and attended the centre alone.

"Security were notified of the unattended child by a passer-by at about 10am.

"They made numerous attempts to locate the owner of the car but were unsuccessful.

"Security removed the child and took him to their office where they were met by police," he added.

The woman, from Doncaster, was eventually found at 11am and spoken to by police.

Ambulance crews checked over the child, declaring him in good health.

Police officers say they expect to charge her with the unattended child offence and learner driver fail to be accompanied by licensed driver.

jon.kaila@news.com.au