The pilot of the Piper Pawnee glider tug reported that soon after takeoff, at about 200ft AGL the engine lost power. The pilot of the glider being towed realised there was a problem and released the tow line. The glider was able to return to the airfield for a normal landing. The Pawnee collided with the tops of trees as the pilot attempted to force land into a paddock. The aircraft subsequently landed heavily and suffered substantial damage. The aircraft was fitted with one 84 litre fuel tank in each wing. The investigation found that the left tank was empty while the right tank was approximately three quarters full. The fuel selector was found selected to the empty left tank. The pilot advised that he had refuelled the aircraft the previous night with 55 litres of fuel. He was unable to recall whether he had put any of that fuel in the left tank. He said that he did not physically check the fuel quantities after the refuelling or during the daily inspection on the morning of the accident. He advised that he conducted the first flight of the day with the fuel selector to the right tank. He noticed during that flight that the aircraft appeared to fly right wing heavy. For the next flight, the accident flight, the pilot changed the fuel selector to the left tank. He was unable to explain why he had selected the left tank when he knew that the right wing was heavy. He did not check the fuel quantity gauges when he changed the selection. It was reported that a fuel stain had been noted under the aircraft while it was in the hangar prior to the days operation. No investigation was carried out to determine if the stain was as a result of a fuel leak. The gliding club has required the pilot to undertake a flight review with an emphasis on fuel management and pre-flight inspection procedures. The club is also to require all tug pilots to undertake a session on tug operating procedures as a part of their biennial flight review.