Tasmanian police have been left red-faced by a signage mishap on random breath-testing vans which encourages people to drink drive.

The vans have been emblazoned with the message: "Real mates don't let mates drink drive."

The slogan painted on the sides of vans used throughout the state shortens to "Real mates drink drive" when the sliding doors are open.

The signage was part of a major campaign by the Road Safety Advisory Council.

The Police Department has told officers to remove the slogans by the end of the week.

The department say it is up to the council to pay for the new paint job.