Rickie Lambert scored a second-half hat-trick as leaders Southampton notched their 20th successive home win.
Lambert opened the scoring with an emphatic header just after half-time and added two more from penalties.
Veteran Brighton defender Mauricio Taricco was sent off for disputing the first penalty and thereafter the visitors fell apart.
Fouls by Lewis Dunk and Inigo Calderon, the latter on Lambert himself, helped him take his season's tally to 14.
The win, which maintains Southampton's five-point cushion over West Ham at the top of the Championship, had not looked as if it would be easy to come by in a first half that saw resolute defending from the visitors.
But Saints found a way through four minutes after the interval when right-back Frazer Richardson swung a deep cross to the far post and striker Lambert powered a header past Steve Harper.
It got worse for the visitors when referee Peter Walton pointed to the spot in the 57th minute after defender Dunk brought down Jose Fonte.
Dunk was booked for the foul but Taricco's protests brought the 38-year-old Argentine assistant manager a straight red card.
Lambert converted, before a fingertip save by Harper denied him a third. But the respite was short-lived as he completed his treble in the 69th minute, again from the spot, after he was fouled by Calderon.
Defeat capped a tough week for Brighton manager Gus Poyet after he waded into football's racism row by defending his fellow Uruguayan Luis Suarez .
Live Text Commentary
Full Time The referee ends the match.90:00 +4:06
The ball is crossed by Frazer Richardson, comfortable save by Steve Harper.90:00 +2:56 Booking
Booking Ashley Barnes receives a yellow card.90:00 +2:11
Close range header by Lee Barnard goes over the crossbar.90:00 +0:16
Ashley Barnes fouled by Morgan Schneiderlin, the ref awards a free kick. Direct effort from the free kick comes in from Craig Noone.89:58
Craig Noone fouled by Jose Fonte, the ref awards a free kick. Free kick taken by Craig Noone.88:28
Marcos Painter concedes a free kick for a foul on Richard Lambert. Free kick taken by Frazer Richardson.87:28
Steve De Ridder takes a shot from just outside the penalty area clears the crossbar.85:29
Richard Lambert takes a shot. Save by Steve Harper.84:36
Unfair challenge on Marcos Painter by Lee Barnard results in a free kick. Lewis Dunk takes the free kick.83:45
Kelvin Davis takes the free kick.83:45 Booking
Booking Craig Noone goes into the book.83:33
Free kick awarded for a foul by Craig Mackail-Smith on Jos Hooiveld.82:53
Daniel Fox crosses the ball.81:45
Free kick awarded for an unfair challenge on Craig Mackail-Smith by Jose Fonte. Centre by Craig Noone, Lewis Dunk produces a header from inside the six-yard box that clears the bar.80:43 Substitution
Substitution Lee Barnard is brought on as a substitute for Guly Do Prado.77:51
Guly Do Prado gives away a free kick for an unfair challenge on Gordon Greer. Direct free kick taken by Steve Harper.76:33
Daniel Fox gives away a free kick for an unfair challenge on Craig Mackail-Smith. Direct free kick taken by Liam Bridcutt.75:53 Substitution
Substitution (Southampton) makes a substitution, with Steve De Ridder coming on for Adam Lallana.72:59
Effort on goal by Guly Do Prado from just inside the box goes harmlessly over the target.
Effort on goal by Jack Cork from just inside the box goes harmlessly over the target.68:46 Goal scored
Goal! - Richard Lambert - Southamp'n 3 - 0 Brighton Penalty taken right-footed by Richard Lambert and scored. Southampton 3-0 Brighton.67:30 Booking
Booking Inigo Calderon goes into the book.67:15
Inigo Calderon challenges Richard Lambert unfairly and gives away a Penalty.65:26 Substitution
Substitution Matthew Sparrow replaces Alan Navarro.65:26 Substitution
Substitution Ashley Barnes replaces Billy Paynter.64:26
Daniel Fox takes the free kick.64:26 Booking
Booking Alan Navarro receives a yellow card.64:12
Alan Navarro concedes a free kick for a foul on Jack Cork.62:58
Effort on goal by Richard Lambert from deep inside the penalty area misses to the right of the target.62:35
Headed effort from inside the penalty area by Jose Fonte misses to the right of the target.62:08
Inswinging corner taken by Daniel Fox.59:21 Substitution
Substitution Morgan Schneiderlin replaces Dean Hammond.59:21
Inswinging corner taken by Craig Noone.57:39 Substitution
Substitution Ryan Harley goes off and Inigo Calderon comes on.57:39 Goal scored
Goal! - Richard Lambert - Southamp'n 2 - 0 Brighton Richard Lambert scores a power penalty. Southampton 2-0 Brighton.55:19 Dismissal
Dismissal Red card for Mauricio Taricco.55:05 Booking
Booking The referee shows Lewis Dunk a yellow card for unsporting behaviour.54:29
Lewis Dunk challenges Jose Fonte unfairly and gives away a Penalty.51:28
Steve Harper takes the free kick.51:28 Booking
Booking Dean Hammond booked for unsporting behaviour.49:36
Free kick awarded for a foul by Frazer Richardson on Craig Mackail-Smith. Free kick taken by Ryan Harley.48:20
Frazer Richardson provided the assist for the goal.48:20 Goal scored
Goal! - Richard Lambert - Southamp'n 1 - 0 Brighton Richard Lambert scores a headed goal from close in. Southampton 1-0 Brighton.45:11
Richard Lambert challenges Marcos Painter unfairly and gives away a free kick. Direct free kick taken by Steve Harper.45:01
The game restarts for the second half.45:00 +2:12 Half time
Half Time The ref blows to end the first period.45:00 +0:12
Short corner taken by Daniel Fox.42:17
Ryan Harley delivers the ball, Jose Fonte makes a clearance.38:46
Alan Navarro fouled by Jack Cork, the ref awards a free kick. Free kick taken by Steve Harper.37:07
Outswinging corner taken from the left by-line by Daniel Fox, Richard Lambert takes a shot. Save made by Steve Harper.35:05
Free kick awarded for a foul by Guly Do Prado on Lewis Dunk. Lewis Dunk takes the direct free kick.30:09
Free kick awarded for a foul by Richard Lambert on Craig Mackail-Smith. Steve Harper takes the free kick.29:49
Richard Lambert takes a shot. Save by Steve Harper.29:37
Alan Navarro gives away a free kick for an unfair challenge on Jack Cork. Jack Cork restarts play with the free kick.28:48
Corner taken by Daniel Fox, Ryan Harley makes a clearance.23:06
Steve Harper takes the free kick.23:06 Booking
Booking Booking for Guly Do Prado for unsporting behaviour.22:50
Foul by Guly Do Prado on Marcos Painter, free kick awarded.19:10
Unfair challenge on Richard Chaplow by Marcos Painter results in a free kick. Direct free kick taken by Frazer Richardson.17:06
Inswinging corner taken left-footed by Daniel Fox, save by Steve Harper.14:26
Craig Noone takes a shot from just outside the penalty area which clears the crossbar.13:06
Daniel Fox concedes a free kick for a foul on Craig Noone. Gordon Greer takes the direct free kick.11:40
Lewis Dunk challenges Guly Do Prado unfairly and gives away a free kick. Frazer Richardson takes the direct free kick.11:05
Guly Do Prado takes a shot. Save made by Steve Harper.9:45
A cross is delivered by Daniel Fox, Gordon Greer manages to make a clearance.7:43
The assistant referee signals for offside against Ryan Harley. Jos Hooiveld takes the free kick.5:46
Richard Lambert concedes a free kick for a foul on Lewis Dunk. Liam Bridcutt restarts play with the free kick.4:36
Corner taken right-footed by Ryan Harley, Header from deep inside the penalty area by Gordon Greer goes harmlessly over the crossbar.1:20
Billy Paynter gives away a free kick for an unfair challenge on Richard Lambert. Jose Fonte restarts play with the free kick.0:00
The referee gets the game started.
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