Almost $600,000 worth of cannabis has been found in the boot of a car in far north New South Wales.

NSW Police said the 70kg of prohibited drug was found in four sports bags in the boot of the Mount Tamborine man's car at Sleepy Hollow, near Tweed Heads on Friday afternoon.

(NSW Police)

The car came to police attention after it was seen erratically speeding up and slowing down on the M1 motorway, travelling northbound.

The 27-year-old driver was accused of commercial drug supply and dealing with the proceeds of crime and refused bail to appear at Tweed Heads Local Court on Monday.