McLaren's Lewis Hamilton will start from last place in his first race as Formula One world champion after suffering a gearbox failure in Australian Grand Prix qualifying on Saturday.

The 24-year-old Briton, who won from pole position in Melbourne last year, did not take part in Saturday's second stage of qualifying after finishing 15th in the first session.

"A gear catastrophically failed," McLaren team principal Martin Whitmarsh told reporters.

"We will be changing the box so we're going to take the hit of a gearbox change so Lewis will start from 20th place tomorrow."

Under Formula One regulations, gearboxes must last four successive races with a five-place penalty on the starting grid for any unscheduled changes.

Hamilton sounded calm in the face of his worst Formula One qualifying performance.

"I don't really have a game plan, just go for it," he said. "It can't really get worse than last place so we'll do the best job from there.

"We are a bit quicker than some of the other guys in front of us and we have to make sure that we extract the best from our strategy ... its a challenge and I'm looking forward to it."