Auckland Council is offering advice for drivers as it cracks down on unwanted window washers.

Six months after its new bylaw came in, it's ditching the softly-softly education approach and warning it'll prosecute repeat offenders.

It says anyone who encounters a window washer should make it clear if they don't want their car window washed.

The Council advises rolling up the window and not engaging in conversation.

If that doesn't stop them and the person is intimidating or demanding money, the Council wants people to complain by calling 09 301 0101.

It also suggests taking a picture of the person on their phone, to send to the Council or police.

And if there is criminal behaviour, such as assault or wilful damage, of call 111.