The Seagulls should have won this but Glenn Murray's 77th minute penalty was saved by Kasper Schmeichel only for Vicente Iborra to net an 83rd minute.
Jamie Vardy then compiled Brighton's misery in the 95th minute when he tapped in from Demarai Gray' cross.
But just as Brighton looked as though they would be forced to settle for a draw Iborra popped up in the 83rd minute to head in from Ben Chilwell's cross.
It was hard on the Seagulls, who deserved at least a point from this match.
And while Wilfred Ndidi's late red card for Leicester gave them a numerical advantage, the best they could muster was Gross's free-kick that was tipped over by Schmeichel.
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Vardy then added insult to injury when he poked in at the far post for the most undeserved of victories.
Brighton made a good start and could have been ahead as early as the 13th minute when Jurgen Locadia crossed for Jose Izquierdo only the pass was too long for the out-stretched winger.
GUCCI NDIDI Wilfred Ndidi knew he'd made it when he could afford to buy a Gucci top
Leicester then squandered their best effort of the first half when Iborra's header from Marc Albrighton's cross lacked power and direction to beat Matt Ryan.
The Foxes were then given a real let off when Murray missed two cracking chances for Brighton.
First, he picked up a loose ball from Harry Maguire and raced forward only fire over the crossbar.
He was then played through by Pascal Gross and, despite a hint of offside, managed to plant his shot wide of Schmeichel's post.
After the restart, Izquierdo's selfishness denied Brighton another crack, as he ran into trouble while Murray, who was unmarked in the box, was stood screaming.
Lewis Dunk then headed wide from Gross's free-kick as the home side saw another chance go begging.
Brighton's failure to score finally caught up with Leicester as Jamie Vardy almost deflected the ball into the net with a backheel.
Izquierdo was then sandwiched by Wilfred Ndidi and Maguire and referee Chris Kavanagh pointed to the spot.
But Murray's penalty kick was well saved by Schmeichel to earn his side a share of the points.
It then got worse for Brighton when Iborra fired in to put Leicester ahead.
Ndidi’s sending off nearly gave them a way back, but Vardy made sure the three points went back up north.
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