Furious Spurs players surrounded Webb after his controversial decision
Referee Howard Webb has admitted he should not have awarded the penalty that reinforced Manchester United's stranglehold on the Premier League.
Tottenham led 2-0 at United on Saturday when Webb ruled Heurelho Gomes had fouled Michael Carrick, and the hosts went on to win the match 5-2.
Webb told the BBC: "I've looked at it again and I think it was a mistake but we make these decisions honestly.
"It's not always easy to see the way the play pans out from pitch level."
Interviewed by BBC Radio Cambridgeshire, the 37-year-old added: "I could see the Manchester United player touch the ball and saw him get clattered by the goalkeeper but didn't see the extra deviation from the goalkeeper's fingers touching the ball.
"I'm disappointed as I always strive for perfection. I'll look at the tape in detail later in the week and try to avoid it happening again in the future.
"I never want to have a negative impact on a game and I get no pleasure from not reaching the high standards we set ourselves.
"But show me a man who's never made a mistake and I'll show you a man who's done nothing."
Meanwhile, it has emerged Spurs midfielder Jermaine Jenas could face disciplinary action over his comments about Webb's decision.
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