Liverpool's hopes of qualifying for the Champions League suffered a major setback as struggling Wigan punished an insipid display by Rafa Benitez's side.
The visitors' out-of-sorts performance was summed up four misses by Fernando Torres, who hit the post early on.
A Dirk Kuyt mistake led to Wigan's goal, with Emmerson Boyce then crossing and Hugo Rodallega volleying home.
Charles N'Zogbia almost added a second for Wigan when he broke clear and the home team held on for a deserved win.
N'Zogbia, Rodallega and James McCarthy were outstanding for Roberto Martinez's side as Wigan troubled Liverpool with their pace and no little skill.
Not for the first time this season, Liverpool were well below par and five yellow cards, including bookings for Torres and Steven Gerrard late on, summed up a miserable Monday for the Merseysiders.
They remain just a point behind Tottenham and Manchester City in the race for the top four, but have played 29 games to Spurs' 28 and City's 27, while Aston Villa in seventh are three points behind with three games in hand.
But while Benitez's side need to find form fast as they embark on a run in that includes a trip to Manchester United and an Anfield meeting with Chelsea, Wigan can approach the final games with renewed confidence.
The Latics had won just once in the league in 2010 to fall to within a point of the relegation zone, yet victory saw them climb to 14th with two of their next three games against fellow strugglers Bolton and Burnley.
As both teams came to grips with Wigan's relaid pitch it was Liverpool who started the brighter, their initial attacking strategy to bypass midfield with both Jamie Carragher and Gerrard launching passes to try and release Torres.
That initial spurt of pressure saw Liverpool win a corner with Maxi Rodriguez heading the ball to Torres, but the Spanish striker's volley struck the post.
Having survived that scare, Wigan started to give Liverpool a few things to worry about.
Chief pest to the Liverpool defence was N'Zogbia, who after almost releasing Rodallega with a clever reverse pass, flashed a couple of dangerous crosses across the Liverpool defence.
Symptomatic of Wigan's growing dominance were the yellow cards dished out to Emiliano Insua, Lucas and Sotirios Kyrgiakos.
Openings for Liverpool were proving rarer to spot, though Yossi Benayoun's trickery saw him break clear and tee up Gerrard, who was unable to get his shot on target after his initial effort was blocked by Paul Scharner.
Gerrard and Lucas had been guilty of giving the ball away and the next Liverpool player to do so was Kuyt, an error that led to Wigan's opener.
Boyce pounced on Kuyt's mistake and with the outside of his right foot curled in a cross that Rodallega cleverly touched past Pepe Reina.
Just before the break, Torres glimpsed a sight of goal, but under pressure from Gary Caldwell steered his header over the bar.
That chance was created by Rodriguez and soon after the interval the two former Atletico Madrid team-mates were at it again, with the same result - Torres putting the ball over the bar, this time with a shot.
Soon afterwards Benitez introduced Glen Johnson for Lucas, as the England full-back returned to action for the first time since late December.
Rejigged, but not revived, and almost immediately Liverpool suffered another scare when Marcelo Moreno blocked Carragher's clearance and with the ball looping towards the goal Kyrgiakos had to head away from under the bar.
Liverpool might have dominated possession in the second half but Wigan always threatened on the counterattack with N'Zogbia scampering clear and wriggling a shot past Reina, who was relieved when Scharner was unable to force the ball home at the far post.
With a quarter of an hour to go Torres missed his fourth reasonable chance, volleying narrowly wide after Kuyt headed the ball back to him following Insua's cross, one of the rare fluid pieces of Liverpool play.
Torres's night of frustration etched up a notch when he was booked for a poor tackle on Boyce, with Gerrard becoming the fifth Liverpool to be yellow carded for an equally poor challenge on McCarthy.