A window washer has been seriously injured in south Auckland after being hit by a car.

The crash happened at 10.46am on Monday at the intersection of Great South Rd and Te Irirangi Drive in Manukau.

The man was believed to be washing car windows at the time, senior sergeant Ian Brenchley said.

He was taken to Middlemore Hospital with serious injuries.

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Lanes were briefly blocked but cordons had been lifted by 12.30pm, police said.

Traffic was flowing freely through the area.

The police, local politicians and the Manukau Central Business Association have been vocal in their opposition to window washers.

They say the washers put themselves and motorists in danger and encourage drivers not to pay them.