Lewis Hamilton's Formula One title challenge took a massive hit on Sunday after the McLaren driver was forced to retire when leading the Singapore Grand Prix.

The Briton, who had won two of the last three races, started on pole and was ahead of Red Bull's Sebastian Vettel in second when a gearbox issue left his McLaren stuck in neutral at the start of lap 23.

Hamilton nursed the car into a run-off area as Vettel surged into the lead. The Briton, 37 points behind championship leader Fernando Alsono at the start of the race, got out the car and walked slowly away with his hands behind his back.