Town missed out on the chance to go clear at the top of the Championship, going down in a thriller at the Amex.
In a first-half of sensational goals, Sam Baldock gave the Seagulls the lead before Daryl Murphy levelled with his 18th goal of the season.
Joao Teixeira then took centre stage with a brilliant quick-fire double before the break to put the home side in command and although Freddie Sears’ first goal for the Club set up a nervy finish, Blues couldn’t conjure up a third.
Town made one change from the side that beat Millwall at the weekend, Cole Skuse returning from illness to replace Stephen Hunt in midfield. New signing Paddy Kenny taking his place on the bench.
Former Blues’ loanee David Stockdale lined up in goal for the home side who had new arrival Leon Best among their substitutes.
Teixeira escaped down the left in the game’s first attack of note, his pass inside dealt with by Christophe Berra, who then had to react to the threat posed by Rohan Ince’s ball over the top aimed at Chris O’Grady.
Kevin Bru sent Murphy clear on the left flank in Town’s first foray forward, his cross over the head of the supporting Noel Hunt.
Murphy saw his shot deflected to earn Town a corner, the striker heading over from the flagkick.
Luke Chambers was forced to put the ball behind from O’Grady’s fierce cross, Inigo Calderon getting on the end of the corner without troubling Bart Bialkowski.
Stockdale had to be alert to gather from Paul Anderson’s delivery, but it was the Seagulls who struck first on 18 minutes, Baldock cutting in from the left and sending a right foot rocket past Bialkowski.
Three minutes later Town were level, Hunt’s cross was volleyed in superbly by Murphy at the near post.
Berra sent a header wide after Stockdale’s punch had fell to him on the edge of the box, Hunt crowded out as he got on the end of Murphy’s lay off.
Hunt was in the thick of the action at the other end, heading off the line from Ince, Aaron Hughes’ follow up header landing on the roof of the net as the entertainment continued at a freezing Amex.
O’Grady fired over from 10 yards after Town struggled to clear Danny Holla’s free-kick, Hughes’ header tipped over by Bialkowski at full stretch.
Brighton edged in front again on 40 minutes and again it was a sensational strike that found the back of the net, Teixeira doing the damage from 25 yards, his shot taking a slight deflection off Skuse.
It was Teixeira who struck again with the last kick of the first-half, the Liverpool loanee showing his class with a first time finish from the edge of the box to convert Joe Bennett’s cross.
Mick McCarthy introduced Sears into the action five minutes after the break, Anderson making way as the Town boss shuffled his pack.
O’Grady continued to be a threat for the home side and saw a shot cannon off Berra towards goal, Bialkowski holding firm to pluck the ball out of the air on his line.
O’Grady dragged his shot wide after a flowing Brighton move, Sears denied at the other end by Hughes’ timely challenge inside the box as he looked to reduce the arrears for Town.
Bialkowski kept Blues in the game, saving brilliantly from Baldock after great work from Teixeira down the right as the hour mark passed, Town making a second change with Noel Hunt replaced by Teddy Bishop.
Stockdale plucked Jay Tabb’s cross out of the air, Bishop then denied by Gordon Greer as he weaved his way into the box before Tabb was replaced by Stephen Hunt.
Town found that lifeline on 77 minutes, Sears getting on the end of Kevin Bru’s pass to fire past Stockdale and set up a grandstand finish.
Murphy jabbed his shot just wide after good work from Tyrone Mings had caused problems in the Brighton defence as Blues pushed forward for an equaliser but Chris Hughton’s side held on as Town went down to only a fifth Championship defeat of the season.