Resurgent Liverpool looked to be heading for a third consecutive Premier League victory when two Steven Gerrard penalties put them in command at half-time on New Year's Day.
Bottom-of-the-table Leicester understandably felt aggrieved with the first of those spot-kicks, when referee Mike Jones adjudged Wes Morgan to have handled Raheem Sterling's cross but the ball struck the defender in the face.
Gerrard, who also scored in Liverpool's 3-1 win at Leicester last month, tucked home the resulting spot-kick and struck again from 12 yards after Danny Simpson had handled.
But Nigel Pearson's strugglers were in no mood to feel sorry for themselves and two goals in as many minutes from Nugent and Schlupp salvaged a point at Anfield.
Leicester's fightback came on the back of a victory at Hull City that ended their dismal 13-game winless run and will give them great heart in their battle to avoid the drop.
A point for Liverpool ensured they have suffered only one defeat in 11 games, but the draw will undoubtedly be viewed by manager Brendan Rodgers as two points dropped.
Riyad Mahrez's strike at the KC Stadium ended Leicester's long wait for a win and the Algeria international almost gave the visitors a shock lead at Anfield after only two minutes.
Liverpool goalkeeper Simon Mignolet was clearly expecting Mahrez to cross a free-kick from long range, but the winger opted to shoot and his left-footed effort came back off the post.
It was Liverpool who were in front after 17 minutes, though, courtesy of a highly controversial penalty as referee Jones adjudged Morgan to have handled Sterling's cross when the ball struck the Leicester captain in the face as he slid on the ground.
Gerrard made no mistake with the resulting spot-kick, which he buried into the bottom-right corner of the net.
Leicester had every right to feel hard done by with Liverpool's first penalty, but there was no doubt Simpson handled when referee Jones pointed to the spot five minutes before the break and the full-back was punished when Gerrard sent Ben Hamer the wrong way from 12 yards out.
Jordan Henderson almost had a contender for goal of the season when he showed great technique to meet a Gerrard corner with a volley that flew narrowly wide shortly before the break.
Adam Lallana limped off 10 minutes into the second half and Leicester were back in the game just before the hour when Jamie Vardy, preferred to leading scorer Leonardo Ulloa in the starting line-up, chested the ball down and Nugent beat Mignolet with a fine half-volley from 20 yards out.
And Liverpool were stunned two minutes later as Mahrez picked out Schlupp and he equalised with a left-footed drive from outside the area.
Substitute Fabio Borini fired over the crossbar after Sterling had picked him out inside the penalty area and Hamer denied Henderson five minutes from time.
Borini went down under a challenge from Morgan in the box late on, but Jones this time saw nothing untoward before Lazar Markovic headed wide as Leicester held on for a precious point.
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