MONTREAL - Jenson Button called it the most eventful and best victory of his Formula One career.

The British driver for McLaren Mercedes needed to make six pit stops, but battling back to take advantage of a mistake by F1 leader Sebastian Vettel's Red Bull to pass on the final lap and win a rain-soaked Canadian Grand Prix on Sunday.

Then he had to go visit the race stewards to explain how he bumped Ferrari ace Fernando Alonso off the track on the 37th lap, but they decided to take no action.

"A great race -- to be on the podium was an exceptional result," the 31-year-old said after his first victory of the Formula One season and the 10th of his career. "I had to fight my way through from last position.

"It's definitely my best race."

The day was marked by a two hour five minute rain delay after 24 laps when an already wet track was deluged with rain. And while the cars were regrouped five times behind the safety car, pole-sitter Vettel held his lead easily on each restart.

But after the safety car went off the track the last time after 61 laps, Button was flying, using the new Drag Reduction System (DRS) -- a temporary speed jolt only allowed on two straightaways -- to pass his rivals and gain ground steadily on Vettel.

The German mistimed his brakes slightly and swung a little wide near Turn 5 on the 14-turn Circuit Gilles Villeneuve, losing a split second by going off the dry racing line onto a wet spot. And Button roared past for the lead.

"To make a mistake on the last lap, probably the only mistake I made in the whole race, is not very sweet, but that's how it goes," said Vettel, who had won the last three races and five of seven this season. "We're all pushing hard and sometimes mistakes happen. I admit I went a little wide.

"I should have pushed harder after the safety car (to build a bigger lead). I was probably a bit too cautious there."

It was still a good day for the leading Red Bull team, with Vettel second and Mark Webber third, and they stretched their lead in constructors' standings to 69 points over McLaren Mercedes.

The 42-year-old seven time world champion Michael Schumacher came fourth for Mercedes GP while Vitaly Petrov was fifth for Lotus Renault.

Felipe Massa was sixth for Ferrari, Kamui Kobayashi seventh for Sauber, Jaime Alguersauri earned his first points of the season in eighth for Toro Rosso, Rubens Barrichello was ninth for Williams and Sebastien Buemi took the last point for Toro Rosso.

Vettel retained the lead in drivers standings with 161 points, while Button moved into second place with 101 with Webber third at 94.

Defending Canadian Grand Prix champion Lewis Hamilton of McLaren Mercedes, whose season looks to be spiralling out of control, failed to finish and dropped to fourth with 85 points.

Button looked amazed to win a crazy race, where he said visibility was sometimes nil as tires threw up spray.

On the eighth lap, his teammate Hamilton tried to force past him on the inside and brushed a wall, ending his race. Hamilton was already being looked at by stewards for sending Webber into a spin on the first lap.

Button also had a drive-through penalty after 12 laps for speeding behind the safety car.

And when racing resumed after the rain delay, Button got tied up with Alonso on a turn and put the 2005 and 2006 F1 champion, one of the quickest on the track all weekend, out of the race.

Each time he lost several positions, but kept battling back.

"I enjoyed it very much coming through the field," said Button, who also heaped praise on his pit crew. "Fighting your way through the field is almost as good as winning the race.

"I'll remember this a long time."

Hamilton was apologetic later and said was glad he didn't take Button out of the race, but it was a second event in a row in which his conduct was called into question. In Monaco two weeks ago, the 2008 F1 champ was assessed two drive-through penalties for on-track incidents, then flirted with a suspension for a post-race tirade against the stewards.

Racing legend Niki Lauda reportedly told German TV that Hamilton is "completely mad."

Webber wasn't thrilled to have been spun around on the first real lap.

"I think Lewis thought the checkered flag (the end of the race) was in turn three," the Australian said dryly. "I tried to give him some room.

"I know it's easy to clip someone but I think it was a bit clumsy that early in the race. It was a tough Grand Prix for all of us. Clearly, it was Jenson's day, and great points for us as a team."

It was the first F1 race on a wet track this year. It wasn't raining at the start, but stewards decided to begin the race behind a safety car because of the wet track.

But no matter how hard it poured or how long the delay dragged on, most of the fans in the packed grandstands were equipped with rain gear and stayed in their seats throughout the deluge as workers used sweepers and squeegees to push water off the asphalt.

It was the first Canadian Grand Prix run in the rain since 2000, when it started pouring on the 44th lap but the event was able to be completed. Michael Schumacher won.

Notes: Among celebs spotted on paddock row were singer Rihanna (at the McLaren garage consoling Hamilton), rapper/actor Ice-T and director George Lucas. . . Pedro de la Rosa, filling in at Sauber while Sergio Perez recovers from concussion symptoms, made his first start since Italy 2010.