Mauricio Pochettino’s men completed a disastrous week as they threw away another lead to lose 2-1 to the Foxes on Saturday.
Harry Kane put Spurs 1-0 up, just as he did in their 2-2 Champions League draw with Olympiakos, and they thought they had scored another when Serge Aurier’s strike was eventually ruled out by VAR.
Son Heung-Min was ruled to be fractionally offside in the build-up to the goal, which would have put Spurs 2-0 up.
Instead Ricardo Pereira and James Maddison struck to win it for the Foxes, who moved up to third in the Premier League while Tottenham back in seventh after just one two wins from their opening six games.
And following the defeat at the King Power Stadium, Vertonghen said: “It’s painful. Man City probably felt the same in the quarter-final of the Champions League last season. It was the same distance [the marginal offside].