McLaren's Lewis Hamilton will start from the back of the grid at the Australian Grand Prix following a gearbox change.

The Briton was unable to complete a single lap in Q2 after being hit by a gearbox failure at the end of the first qualifying segment.

Although McLaren could have changed the gears and avoid a penalty, the team has decided to replace the gearbox altogether, meaning Hamilton will get a grid penalty.

"It was a gear failure and although we are allowed to change gears under the regulations, we will change the gearbox," said team boss Martin Whitmarsh.

Under the current rules, gearboxes must last for four grands prix.