The SPCA is investigating claims a man used an automatic car wash with his dog locked in a kennel on the back of his car.

The alleged incident happened Monday night in Invercargill, with a witness saying high pressure soap and water was spraying into the dog's face.

A spokesperson told Newshub SPCA inspectors will undertake a full investigation into the alleged incident.

SAFE ambassador, Hans Kriek, said the accusation is shocking.

"I can't really fathom why somebody would do that, [it's] just clear that it was going to be very bad for the dog and highly distressing."

Mr Kriek said he's never heard of something so appalling, but it could have been an awful mistake.

"What you often find is that a lot of people that are cruel to animals are not deliberately cruel to animals but they're just ignorant about the needs of the animal," he said.

If it wasn't an accident, the man must be held to account, Mr Kriek said.

Newshub.