Why Max Key was thrilled to see his dad doing chores

John Key - his car's not dirrty (Max Key / Facebook)
John Key - his car's not dirrty (Max Key / Facebook)

John Key has revealed why his son Max seemed so happy to see the Prime Minister washing a car at the weekend.

It was Max's car.

In a clip posted to Facebook on Sunday, Max dances to pop song 'Car Wash' and hip hop music, while his dad scrubs and soaps up a car on the family's driveway.

"Bronagh and I had gone to the gym on Sunday morning, so I'd come back and been for a run, and I said to her 'look, I've got to clean out the garage', which she wholeheartedly agreed," Mr Key told More FM on Thursday morning.

"I chucked on my gumboots and said well, I may as well have a shower after I've done that, and I'll wash the car."

He only planned to wash his and Bronagh's at first. Then he saw the state of Max's vehicle.

"I looked over and there was his car - and you know, you have that sort of, 50 percent of your brain is screaming 'clean it' because everything else is tidy and this isn't, and the other 50 percent is thinking, this is sending all the wrong messages.

"I was thinking was he was upstairs, there's no chance of him coming down. He won't even notice and I'm not going to tell him. I'll just do it and it'll make me feel better."

Max did see, and asked the Prime Minister if he was trying to get his vote before getting his groove on to Christina Aguilera and Missy Elliott.