A draw in the final game of the group stage will be enough for Spurs to make it to the knockout phase.
Spurs knew victory would guarantee a place in the last 16 but they laboured for long periods before being denied a last-ditch winner when Harry Kane's strike was ruled out for being in line with the goal.
The home fans jeered at the first half display that brought loud jeers, but they were silenced in the 22nd minute by a fine low shot by Marcus Edwards.
Spurs were much improved after the break but they were grateful to a crucial save by keeper Hugo Lloris from a substitute who also shot wide.
They were able to take advantage of the two escapes, as they were able to score from a corner 10 minutes from the end of the game.
Kane thought he had taken it with the last kick, but the VAR disagreed.
Spurs were left regretting the intervention of VAR that denied them the win, but they must also rue another slow start that allowedSporting to take control for the first 45 minutes.
The angry reaction from supporters who had grown frustrated at a series of aimless and misplace passes was indicative of the growing rebellion inside the stadium.
After the break, Spurs came to life and forced Adan into action.
They still looked vulnerable, however, and Lloris came to the rescue with that crucial save from Nazinho, although the Sporting forward should have made no mistake with a second chance which he steered wide of an open goal.
After getting themselves back into the game, Spurs had chances to get the three points that would have made the trip to Marseille a formality, but Eric Dier and Bentancur could not score.
The game ended in a brawl after Conte was sent off for celebrating what he thought was the goal that sealed the knockout place.
The lessons of being punished for leaving it late to kick into gear need to be learned by Spurs.
It was certain that Marcus would score on his return to Spurs, the club where he could not break through despite his talent.
The 23-year-old is fulfilling his potential in Lisbon and following up a fine performance in the first group game, whichSporting won 2-0, with another display rich in promise here.
He was a constant threat in the first half, but after the break he faded as Spurs paid the price for standing off.
Those who remember him from his unfulfilled Spurs career will be impressed by how he performed here, as he is now bolting on attitude to ability.