The Hammers shrugged off their recent home misery by blitzing Gus Poyet's play-off hopefuls with three goals in the first 10 minutes, before finishing them off in the second half.
Portuguese forward Vaz Te started the rout with a quickfire brace before skipper Kevin Nolan added the third.
Vaz Te struck again with a superb scissor kick just after the hour mark to take his tally to five goals in his last two matches.
Carlton Cole added the fifth and Brighton's misery was complete when Gary Dicker put through his own net.
Sam Allardyce's side, who had slipped off the pace following a rotten run of seven home matches without a win, are now just three points behind second-placed Southampton with three games to play.
Poyet, by contrast, has maintained for most of the season his team are not ready for promotion, and they certainly set about proving him right in a disastrous start to the match.
Henri Lansbury set the tone when his shot from the edge of the area hit the crossbar after only 30 seconds.
Two minutes later West Ham were ahead when Nolan robbed Brighton's Spanish midfielder Vicente and played in Vaz Te, who let fly from 25 yards.
His shot had some swerve on it but should not have troubled Peter Brezovan unduly, yet the Seagulls keeper was flapping at thin air as the ball whistled past him.
With West Ham suddenly laying siege to the visitors' goal Brezovan was beaten again in the eighth minute.
Guy Demel launched a deep cross from the right and Vaz Te sneaked around the back to squeeze a header inside the far post.
There was no respite for Brighton with Nolan making it three two minutes later, the midfielder tucking his 12th of the season past the hapless Brezovan after James Tomkins headed Matt Taylor's free-kick back across goal.
The shell-shocked Seagulls eventually managed to stem the flow and even came close to pulling one back before half-time, but Rob Green clawed away Gordon Greer's header with the Seagulls defender claiming in vain that the ball had crossed the line.
But normal service was resumed after the interval with Vaz Te completing his sparkling treble in the 62nd minute.
Cole headed the ball across goal and, as West Ham appealed for a penalty for a push on Lansbury, Vaz Te launched himself in the air and crashed his acrobatic effort into the net.
Two minutes later Cole's shot was deflected off the heels of Lansbury to dupe Brezovan yet again.
And with 11 minutes left Dicker diverted Mark Noble's corner into his own net to seal an emphatic win to take some of the heat off Allardyce - and maybe set a few nerves jangling on the south coast.
