Sir Jackie Stewart has backed Michael Schumacher's decision to retire from F1 for a second time, insisting that it is a move the German should have taken 'a while ago'.

The seven-time champion came out of retirement in 2010 in a three-year deal to help lead Mercedes after it completed its takeover of the Brawn GP team, although he has managed just one podium finish in his three seasons back on track.

Having been replaced by Lewis Hamilton for next year, Schumacher was linked with a switch to Sauber but has instead elected to retire for a second time, with Stewart saying it was overdue.

"His reputation has already been affected by his unsuccessful return to the sport," he told BBC Sport. "People will applaud the decision as it should have happened a while ago.

"The speculation within the whole F1 community has been that Michael should be retiring - and hopefully not for a short period this time. In a way I am sorry Michael came back. Recently he's had too many incidents."

Stewart added that collisions this season with Bruno Senna and Jean-Eric Vergne had been an indication that the time had come for Schumacher to call it a day.

"These two incidents, running up behind other drivers and hitting them at great speed, you might have expected from an inexperienced driver in their first year, but not from one of the great drivers," he said. "These driver errors would just never have happened with the likes of Alain Prost, Ayrton Senna, Nicki Lauda or Jim Clarke. They could have ended in tears.

"There comes a time when everyone recognises it may be time to retire."

Admitting that he felt it would be better for the German to seek a non-competitive role in motorsport, Stewart also said he didn't feel Schumacher could be classed as the greatest driver in the history of the sport despite his record of achievements, given the different eras in which the top names competed.

"His record will, I think, remain unbroken forever," he said. "He's one of the greatest drivers of all time, although it's not possible to say he's the greatest. The number of Grand Prix he's driven are considerably more than anyone else. Juan Manuel Fangio didn't come to Europe to race until he was 39, yet won five world championships. His ratio of wins to races was extraordinarily good.

"Jim Clarke likewise. Myself, I only raced in 99 Grand Prix races but won 27. Although that's nothing like the 91 that Michael has won, the average was good.

"Michael's record in F1, particularly his Ferrari period, was so dominant because the car and engine was unquestionably the best on the grid and there was no doubt about who was number one and got most attention in the team."