Insurance sector lawmaker Chan Kin-por said on Friday that car owners who only have third-party insurance are going to find they aren't covered if their vehicles have been wrecked by floods.

Chan said many cars were completely submerged by water following Thursday night's massive rainstorm and will be deemed to be a "total loss".

"If you bought the comprehensive insurance cover, then you can cover the damage to the car," he said.

"But if you only have third-party cover, then you can only cover accidents arising for hurting third parties."

The legislator also noted that there will be a lot of insurance claims from shops and malls across the city that have been damaged by flooding.