The Ivorian's misguided decision to attempt a pass across his own box was punished by substitute Victor Anichebe, who fired past Simon Mignolet to earn his team a point
Brendan Rodgers' side could have gone four points clear in fourth with a win over a West Brom outfit still looking for a first win under new coach Pepe Mel.
And the visitors appeared to be on course for a 15th league victory of the campaign when Daniel Sturridge put them ahead with a close-range finish midway through the first half.
Liverpool dominated for large periods, but they were left to rue an ill-advised pass from Toure, which allowed substitute Victor Anichebe to level matters after the break with only his second goal since joining West Brom from Everton.
Mel's men could not complete the turnaround, though, with both sides forced to settle for a point that moves Liverpool two in front of fifth-place Everton and West Brom only one ahead of the relegation zone.
Liverpool was unchanged from the 4-0 midweek mauling of local rival Everton, but the visitors struggled to break down West Brom in a subdued start to the contest.
However, they scored with the first real chance of the game after 24 minutes, Sturridge tapping in his 50th Premier League goal from Luis Suarez's magnificent far-post delivery after the Uruguayan had linked up well with Raheem Sterling.
Rodgers' side continued to dictate, with Philippe Coutinho going close from long range, and West Brom's cause was not helped by an injury to defender Jonas Olsson, who limped off five minutes before the interval to be replaced by Diego Lugano.
It took the hosts 42 minutes to fashion a goalscoring opportunity, but midfielder Zoltan Gera’s drive from distance flew well off target.
West Brom made a better start to the second half and would have leveled through Gareth McAuley's close-range header had it not been for a stunning save from Liverpool goalkeeper Simon Mignolet.
Still, the hosts remained fallible at the back, with only the fine reflexes of Ben Foster preventing Suarez from doubling Liverpool's lead just before the hour mark.
Liverpool, though, was made to pay for Suarez's profligacy as West Brom profited from Toure's woeful error. The Ivory Coast international attempted to play a pass across the face of the box, but instead it landed straight at the feet of Anichebe, who steadied himself before firing past Mignolet and into the bottom corner with 67 minutes gone.
That proved to be the last meaningful moment, with West Brom perhaps controlling the close stages without ever fashioning a clear-cut chance to snatch a win.