Rear light problems

Rear lights are working on the bumper but not on the car 300tdi can anyone help

On the 300tdi I'm pretty sure that the rear lights are on two fuses, one for those on the right and the other for the left. That being the case, the faults are more likely to be closer to the bulb holders than the supply.

Check the bulbs, then examine the inside of the bulb holders for corrosion preventing electrical contacts then go looking for earthing problems.

Thanks I'll try that