Drain on Battery

I have an electrical problem with my TR6 and wonder if anyone else has had this problem. If I don't isolate the battery each night it will be dead in the morning. The ignition light on the dash is malfunctioning. When the ignition is in the off position the light is on when it is in the on position it is off. I have removed the bulb to reduce the drain but the battery will still be dead in the morning. We have done some checking and the fuses are operating as they should. Perhaps the problem is in the ignition switch itself. Please advise if you have any suggestions on how to solve the problem.