BARCELONA, Spain (AFP) - Jenson Button and the Brawn GP team swept aside all doubts about their durability as championship contenders on Sunday when they delivered a triumphant performance in the Spanish Grand Prix.

The 29-year-old Englishman claimed his fourth win in five races this season, finishing ahead of teammate Rubens Barrichello as Brawn proved themselves worthy winners in the season's first race in Europe.

Their one-two triumph ahead of the leading Red Bull car driven by Mark Webber confirmed that, even after weeks of developments and revisions by their rivals, Brawn are still the team to beat.

"I'm so happy - once you start winning it is such a great feeling," said British driver Button, who was not even sure he would have a job this year when the former Honda team closed down last November.

"Last year, it felt just the opposite. But when it goes well, it really goes well doesn't it? I'm on top of the world now compared to last year. But I have to say that the whole team did a magnificent job.

"The package we have has definitely kept its advantage and I am grateful for that to the guys working so hard back at our base in Brackley (in England).

I want to thank them and Mercedes-Benz (for the engines) because we could not do it without you."

Brazilian veteran Barrichello, disappointed not to claim his first win for the new Brawn team after making a brilliant start and dominating periods of the race, said he had been let down by his third set of tyres.

"From the first corner, I thought I would win the race - and I pushed as hard as I could - but on my third set of tyres I didn't have the pace of my first or second sets of tyres. I was locking up all over the place."

The Brawn team made a crucial decision mid-race to switch Button from a projected three-stop strategy to a two-stop and this finally gave him an advantage over Barrichello, who stayed on three stops, when the Brazilian was unable to push to the maximum.

Webber came home third to maintain Red Bull's competitive form ahead of team-mate German Sebastian Vettel, who was fourth, Spaniard Fernando Alonso in his Renault and Brazilian Felipe Massa, who slowly rolled over the line as his Ferrari ran out of fuel on the final lap.

Germans Nick Heidfeld of BMW Sauber and Nico Rosberg of Williams were seventh and eighth ahead of defending world champion Lewis Hamilton, who failed to score a point for McLaren Mercedes and now faces an uphill battle to retain his title.

After five of this year's scheduled 17 races, Button leads with 41 points ahead of Barrichello on 27 and Vettel on 23, while Hamilton lies in seventh place with only nine points, 32 fewer than his compatriot.

Hamilton, who struggled throughout the race, said: "Look, of course, as it stands I don't have a car to win the championship.

"I drove my heart out, but what can I do? I have not been given a car that enables me to challenge. I want to congratulate Jenson - he ran a good race - and I just hope I'm up there competing with him soon."

Button came home 13 seconds clear of Barrichello after 66 laps in warm sunshine to claim the fifth win of his career.

On a warmer day than the previous two, with the air temperature at 24 degrees and the track touching 42 degrees, there was a bigger crowd and more atmosphere, but not quite the fervour of previous "Alonso-mania years."

At the start, Barrichello made a storming getaway and took the lead ahead of Button with Massa passing Vettel behind them, thanks to use of the KERS on his Ferrari.

But behind them, a multiple collision triggered by Jarno Trulli's Toyota spinning off and back on to the circuit, removed four cars from the race and brought out the safety car.

The accident happened at the second corner and involved both of the luckless Toro Rosso cars of Sebastien Buemi and Sebastien Bourdais along with Trulli and Adrian Sutil's Force India.

It left mechanical carnage all over the track and it required five slow laps behind the safety car before the mess was cleared up and the racing resumed with a field of only 16 runners.

This was reduced to 15 when the two Finns in the field retired, Kimi Raikkonen with hydraulic problems in his Ferrari and Heikki Kovalainen with gearbox problems in his McLaren.