Jenson Button continued his dominance of this season's Formula One world championship with his fourth win in five races after a superb pit-stop strategy switch at the Spanish Grand Prix.

This was the ninth successive year that a driver has won from pole position at Barcelona's Circuit de Catalunya, but it was no conventional procession from start to finish for Button.

After being passed by Brawn GP team-mate Rubens Barrichello on the run down to the first corner, Button and his team made the call to run from three stops to two early on.

It proved decisive as the 29-year-old did enough when Barrichello made his three trips into the pits to again take the chequered flag at the end of the 66 laps.

Yet despite standing on the top step of the podium for the fourth time this year, Button's lead is only 14 points over Barrichello, who duly claimed second ahead of Red Bull's Mark Webber.

The start to the race was marred by a four-car accident, bringing a swift end for Toyota's Jarno Trulli, Giancarlo Fisichella in his Force India, and the Toro Rosso duo of Sebastiens Bourdais and Buemi.

Williams' Nico Rosberg was the instigator as it was he who gently nudged Trulli off the circuit coming out of the opening chicane.

After running onto the gravel, it was evident Trulli had little traction as he made his way back onto the track as he slid into the on-rushing traffic.

Unable to take evasive action, Fisichella rammed into the side of Trulli, sending both shattered cars careering onto the gravel.

It was remarkable that as passengers at that point they failed to collect any of their rivals because the Bourdais/Buemi encounter was a separate affair.

Driving into the back of young Swiss Buemi, Frenchman Bourdais was temporarily launched into the air, running over the top of the 20-year-old, yet remarkably no driver was hurt.

With debris strewn across the track, world champion Lewis Hamilton was fortunate not to sustain damage, in particular to his tyres.

Starting from 14th on the grid, Hamilton ran over a sizeable piece of bodywork at one point as he attempted to weave his way through, yet emerged unscathed.

However, it relegated him to 16th and last behind the safety car which made an inevitable appearance, and for the fourth race of the five this year given the various incidents that have unfolded.

Hamilton produced a credible drive from such a lowly position, but in finishing ninth, he missed out on what would have been another deserved point.

Instead, he finished a lap down on Button, who finished 13 seconds clear of Barrichello, with Webber in close attendance.

Another mistake from Ferrari at Felipe Massa's second pit stop as his crew failed to put enough fuel in his car, saw him relegated from fourth to sixth in the closing laps.

Massa was told to slow down to conserve fuel, otherwise he faced the prospect of running out before the finish.

It allowed Sebastian Vettel to pass the Brazilian at the start of the 63rd lap to claim fourth, with Fernando Alonso thrilling his home fans with a round-the-outside manoeuvre on the final lap to claim fifth.

At least in taking sixth, Massa has now finally broken his points duck, although he will surely feel aggrieved as he knows he should have had more.

BMW Sauber's Nick Heidfeld and Rosberg completed the top eight of a 14-car field as McLaren and Ferrari suffered further woes.

Heikki Kovalainen retired shortly after the race resumed following the withdrawal of the safety car after it had run for four laps.

As for Kimi Raikkonen, he ground to a halt on lap 18 as his engine lost power, just to add to the early failure of his KERS system.

In the constructors' championship, Brawn GP now hold a 29.5-point cushion over Red Bull Racing, with Toyota 31.5 points adrift.

Button said: "I was switched to cover all our bases. "We thought the three-stop (strategy) was the better, and when I was told we were going to two and I put the fuel on board, it felt very heavy.

"But it worked well and to come away with a win - and they all mean a lot - gives me a lot of confidence for the rest of the season.

"It is a dream come true so far this season. Even when times are tough we are getting the wins.

"When it is good, it's good, just like when it's been bad for us these past couple of years, it was bad.

"But I do feel I'm on the top of the world at the moment."

An unhappy Barrichello, who felt he should have won, remarked: "I had a great start, going into the lead.

"Then I heard they changed his strategy, and I had to keep pushing, but I had problems with my tyres, and it was a struggle to keep the car on the track.

"I'm disappointed I've not won, but it was a great effort from the team."

Webber, who is now fourth in the championship, was naturally happy to have finished on the podium.

He said: "It was a tough first stint, particularly after qualifying, so we did our best to hang in there.

"But then the second, which was long to try and jump others, went extremely well for me.

"It's a good day for the team. We would have liked a few more, but it's 11 and that's a good chunk.

"We'd like to be closer to these guys (indicating Button and Barrichello), but then we are pulling away from the rest of the field."