Spurs thought they had come from behind to beat the Portuguese side and book their place in the Champions League knockout stages when Kane swept home from close range in stoppage time.

But, after a lengthy VAR check, the England captain was ruled to be offside, meaning Spurs will have to avoid defeat away to Marseille next week to qualify for the last 16.

• Champions League groups | Fixtures | Results
• Tottenham 1-1 Sporting - Match report
• How the teams lined up | Match stats

Conte was sent off for his reaction to the decision and will serve an automatic one-game ban, meaning he cannot be present on the touchline in Marseille. He could face extra punishment depending on what is in the referee's match report.

Conte admitted he was still "really upset" when he took his one and only question from reporters in his press conference shortly after full-time. He could yet be investigated for his post-match comments which also depends on the match delegate report.

"All the people came onto the pitch and then the referee decided to send me off," explained Conte. "I think there are moments where you can understand you have just disallowed a regular goal because the ball is in front of Kane.

"You know that I don't comment on the referee's decision but the VAR this season in the Premier League and the Champions League, we are not so lucky.

"I think it creates a big damage. I'd like to see this type of decision with a top team in an important game, I'd like to see if the VAR is so brave to take this decision - I repeat an unfair decision because the ball is in front of Kane.

"Sorry but I'm really upset because sometimes you can accept this situation but sometimes I think it's not good because I don't see honesty in this type of situation and when I don't see this I become really, really upset.

"For the game, I think we played the first half with low intensity and Sporting Lisbon deserved to stay 1-0 up. At the end of the game, after our second half, I think we deserved to get three points. But now for this decision we have to wait for the last game against Marseille."

Conte also urged Tottenham to "speak to the right people", particularly if they end up missing out on qualification for the knockout stages.

He said: "I repeat, this decision creates a big damage. I hope the club understands this and then in the right situation to speak with the people that they have to speak to, otherwise it's only the manager that speaks.

"I think the club must be strong because this situation has created a big, big damage. Now we don't know what happens next week and if we go out then I want to see."

LLoris: VAR is complicated

Tottenham captain Hugo Lloris said VAR decisions are complicated to understand when the margins are so fine.

"When it is so close it is very hard to decide," he said. "It is the technology and we start to get used to it but it is a complicated period that we live in.

"We know the rules obviously. The problem is when you look at the angle of the camera you don't know if the defender's foot is on the same line as Harry Kane's foot, it is very difficult to see.

"Also the line of the ball is a reference but it is difficult to see and to identify the real line. It is hard but it is the technology we have to trust and when it goes against you, you feel it is unfair but when it is on your side, then your feelings are very different."

Why was Kane's goal disallowed?

Kane was behind Emerson Royal when the Spurs wing-back nodded the ball back towards him in the Sporting area. The ball deflected off a defender and dropped in front of Kane, who finished first time to seemingly win the game for the hosts.

However, following a VAR check that took several minutes and left those in the stadium unsure whether Tottenham had indeed sealed their place in the next round, it was determined that Kane was slightly in front of the ball when Emerson headed it in his direction and was therefore offside.

Can you be offside from a backwards pass?

Yes. If the ball is passed backwards but the receiving player is ahead of the ball when it is played, they can still be offside upon receiving it. In this case, because the deflection that took the ball into Kane's path is not considered a deliberate play, Kane's offside position was not reset.

This kind of incident is rarely seen and is no doubt a painful one for Spurs but, despite their protestations - Eric Dier shouted "the ball went backwards!" to officials after the game - this was done by the book.

Dermot says: We've got to trust the system

Was it the right decision?

Former Premier League referee Dermot Gallagher: "Everything depends on the ball. Is Kane behind the ball when it's played by Emerson? It's so, so tight.

"We've got to trust the system. The system says Kane is just in front of the ball so therefore that plays him offside.

"The other thing is, it hits the defender and people say that plays Kane onside. It doesn't because the law says it's got to be deliberately played or the player has got to make a deliberate move to the ball. It struck him.

"The unfortunate thing about this decision is, is it factual? It's not a matter of opinion, it's not a matter of clear and obvious error. It is a factual decision. The decision they've come to is that he's factually offside."

Why did the decision take so long?

Gallagher: "I was watching it live, it seemed an eternity. They've looked at it from all kinds of angles. They've tried to put the lines across, it was tight, there's no doubt about that. From one angle it looks like he's just behind the ball.

"I can understand the fans in the crowd getting more and more frustrated as it went on. When we went into VAR, everyone said if it takes a little bit longer to get a decision right then that's what we'll live with. Nobody anticipated three-and-a-half minutes.

"It just shows it's not as clear-cut or as easy as everyone said. It's frustrating but they have said it's factually offside."

O'Hara: VAR is ruining the game

Former Tottenham midfielder Jamie O'Hara: "VAR absolutely cost us. I've watched it back a hundred times, I've seen the still images, I've seen where they've put the lines, and I'm still not convinced it's offside. I can't see it and I don't know how they came to this conclusion.

"It's just ruining the game, isn't it? Four minutes to look at an offside? It's meant to be done in 30 seconds. It's outrageous and it's just ruined and marred what was a brilliant second half of a Champions League match.

"It's happening all the time now and it's not good.

"The reason we love the game is for those moments. 95th-minute winners, equalisers. If you looked back over the years when we've had those great moments and you stopped and you went through every little thing, so many goals and amazing memories we've had in the Premier League and Champions League would be chalked off.

"VAR is looking at the tiniest and finest margins. It's almost like they are looking to chalk a goal off. I just don't understand that.

"The referee was there. He saw it. The linesman saw it. If it's not completely clear and obvious that Harry Kane was offside, just leave it, it's a goal.

"Four minutes says to me it's not clear and obvious and you don't really know, you're 50:50 on the decision.

"That for me is completely ruining the game for the spectators, for the managers, for the players, for everyone. I'm just sick and tired of it."

Amorim: I like VAR, it's fair!

Sporting boss Ruben Amorim: "I like it (VAR) because it's fair - most of the time. There's a lot of problems sometimes because it's a hard decision but I didn't see the footage. For me it was very good. For Antonio Conte it was very bad. It's football.

"It's a good tool to improve football. For the fans sometimes it's not so good but I think it's fair."