A woman briefly left her trolley unattended while shopping at a Midland supermarket about 11.10am when another woman took the wallet, containing cash and credit cards, which was on the child seat.
Accompanied by a man, she then used the stolen cards to buy items at several stores in the Midland area.
The woman pictured is described as dark-skinned, 27 to 35 years old, of medium build, with dark hair tied back and wearing dark clothing.
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READ NOWThe man is described as dark-skinned, 25 to 30 years old, medium build, wearing a black cap, black Nike long-sleeved jumper, three-quarter length beige shorts, thongs and thick gold chains around his neck.
Anyone with information can make a report online at crimestopperswa.com.au or call 1800 333 000.