Real beat Villarreal to go nine clear
Brazil forward Robinho scored a goal in each half in a pulsating match at the Bernabeu, in which Giuseppe Rossi and Joan Capdevila had twice levelled for third-placed Villarreal.
Dutch midfielder Wesley Sneijder scored the winner as Real made the most of second-placed Barcelona's 1-1 draw away to Athletic Bilbao.
Real's eighth consecutive win puts them on have 53 points, Barca have 44 and Villarreal 38. Atletico Madrid and Espanyol both lost as their vague pretensions of challenging for the title were knocked back even further. Fourth-placed Atletico, on 37 points, fell to a goal from Venezuela striker Juan Arango at Real Mallorca, making it three defeats in a week for Javier Aguirre's side.
Espanyol, a point back in fifth, lost 2-1 at home to Real Betis for their third consecutive league defeat.
Elsewhere, problems mounted for under-fire coach Ronald Koeman as Valencia made it nine games without a win, losing 1-0 at home to promoted Almeria.
Real got the ideal start against Villarreal when Guti picked out Robinho's run with a diagonal pass and the Brazilian's first-time shot flew inside the far post after nine minutes.
But the visitors were back on level terms in the 16th when Italian striker Rossi jinked past Fabio Cannavaro and beat Iker Casillas from the edge of the area.
It was the first goal the Spain keeper had conceded in seven games, but it was his opposite number and former understudy Diego Lopez who was the busier as he denied Michel Salgado and Guti before the break.
Lopez pulled off two saves in quick succession as Real broke away in the 53rd minute but he was unable to stop Robinho's follow-up as the home side restored their lead.
Villarreal defender Capdevila equalised again at a corner in the 75th but a minute later substitute Sneijder raced on to Fernando Gago's ball over the top to beat Lopez again.
Bilbao huffed and puffed to little effect in San Mames and when they did get a clear sight of goal in the first half striker Aritz Aduriz hoisted his shot over the bar with only Victor Valdes to beat.
In the 35th minute, Barca counter-attacked, Deco laid the ball out wide for Bojan Krkic and the 17-year-old scored low in the far corner.
Barca were far from impressive and their grip on the game was broken in the 79th minute when French defender Lilian Thuram turned a low cross past Valdes, under pressure from Bilbao's Fernando Llorente on a counter-attack.