Montoya fended off a ferocious late challenge by McLaren’s Kimi Raikkonen to win by 0.6 seconds with Michael Schumacher’s hopes of a record-equalling sixth victory on the tight and twisty streets thwarted as he finished third for Ferrari, just 1.7secs adrift.

Raikkonen now leads the championship by four points from Schumacher, whose bid to grab the title advantage was ended as he tasted defeat in his new car for the first time, paying for qualifying in fifth spot.

The German’s brother, Ralf, had to settle for a distant fourth despite starting on pole with Fernando Alonso fifth followed by Renault team-mate Fernando Alonso.

McLaren’s David Coulthard, winner twice in the past three years, slumped 23 points behind team-mate Raikkonen after finishing seventh with Rubens Barrichello picking up the final point with eighth spot for Ferrari.

Jenson Button did not start the race after BAR-Honda decided not to risk him following his 180mph crash during final practice yesterday while team-mate Jacques Villeneuve suffered another frustrating afternoon as his engine caught fire.

Jordan's rookie Ralph Firman finished his maiden race on the famous streets of the Mediterranean Principality in 12th spot.

Justin Wilson’s bow ended in retirement for his Minardi.

Montoya snatched what proved to be a crucial second spot at the start of the gruelling 78-lap race, with Raikkonen making a dismal start, then got out ahead of his team-mate Schumacher at the first pit stop.

The lead changed hands regularly during the pit-stop windows before Montoya regained the advantage when Schumacher senior, who looked for a time as though he was on a one-stop strategy, made his second visit to the pit lane with 19 laps left.

Montoya, who suffered a blown engine while leading the last race in Austria, kept Raikkonen at bay to claim only Williams’ second victory in Monte Carlo, emulating Keke Rosberg’s success 20 years ago.

It was also the team’s first victory since Malaysia last year, a run of 22 races, and brought an end to their disappointing start to the campaign with the FW25 which had been mockingly likened to a tortoise by BMW engineers this season.