Workmen who dump trade and commercial waste at household recycling centres to avoid paying charges are being warned they face a crackdown.
Durham County Council says up to 15% of waste taken to household waste centres is trade and commercial waste, mostly soil and rubble, and therefore illegal.
The authority says if it is left unchecked, it could cost it �1m in extra waste management costs this year.
A permit scheme is being introduced to prevent rogue traders using the sites.
More effective
Councillor Brian Myers, cabinet member for waste management, said: "It is essential that we achieve a major reduction in the illegal delivery of soil and rubble from commercial sources."
He said the council had tried to drive away illegal operators, but the problem had still increased by 20% in three months.
The permit scheme will be introduced from 6 December. It means all vans, pick-ups and trailers will be banned from the household waste sites unless they have a permit.