A mom has sparked outrage after she refused to allow firefighters to break into her car to save her toddler son from the heat because the vehicle was too expensive to damage.

The unnamed mother was unable to open the door of her BMW when it accidentally locked itself.

Her three-year-old son was trapped inside and was suffering in the heat as no windows were open.

Firefighters who arrived at the scene in Yiwu city, China, were about to break the glass to rescue the boy - but his mum told them she wanted to wait for a locksmith instead so the car would not be damaged.

Stunned onlookers looked on in horror as the toddler cried inside the vehicle as the oxygen levels rapidly went down.

Despite the mother’s desire to wait, firefighters eventually took matters into their own hands when the boy started to faint and they smashed the glass to rescue him.

One of the firefighters was quoted as saying: “It’s very dangerous to leave children inside cars, especially in such heat.

“It can threaten a child’s life in a very short time.”

The mother was blasted on social media, with one person writing: “The mother shouldn’t have left her kid in the car in the first place. Even if the car did accidentally lock itself.

“What happens if someone breaks the window and abducts the kid?”

Another added: “It looks like the car is her real son.”

Pictures courtesy of CEN