Car stolen as child slept in back seat

A thief is on the run after stealing a car while a toddler was asleep in the back seat in Melbourne's southeast.

The two-year-old boy was left alone with the engine running outside a grocery store on Nepean Highway in Chelsea at 4pm on Sunday while his father went to do some shopping.

The criminal snuck into the front seat of the grey Volkswagen SUV and drove off.

He travelled about 350 metres before stopping to leave the child by the side of a road.

A passerby raised the alarm after finding the distressed toddler wandering next to a busy road.

Police believe it was an opportunistic theft and the man responsible didn't realise there was a child in the car until after he took off.

On Monday, police issued a public appeal to find the grey 2019 Volkswagen Tiguan, which has the licence plate BEL650.

It was last seen in South Oakleigh about 5pm on Sunday, when a person believed to be a passenger from the car used a stolen credit card at a McDonald's restaurant.

It's unclear when the second person joined the driver of the stolen car but police described them as about 20 years old with olive complexion, dark shoulder-length hair and a moustache.

They were wearing a black T-shirt, shorts and a white cap at the time.

Victoria Police said the father left his son alone for just a few minutes with the air conditioning on because he didn't want to wake the sleeping toddler.

Detective acting Senior Sergeant Grant Lewis ruled out laying any charges against the father, saying it was not in the public interest to do.

"I don't want to victim shame or blame, he's very traumatised. He certainly wouldn't do what he did again," he told reporters on Monday.

Kidsafe NSW executive officer Christine Erskine it was very lucky the child was not hurt.

"Nothing is worth the risk of leaving your child unattended anywhere, particularly a younger child, they should be within reach," she said.

"It's very scary to think that these incidents, as rare as they are, do happen because a risk has been taken."