"The referee cannot change that decision once the game has been restarted.
"Football is a human game played at a fast pace where mistakes are made by players and match officials alike.
"We regret this error of judgement and will now work with the officials concerned to determine how this occurred in an attempt to minimise such mistakes in the future."
Former Premier League referee Graham Poll said the decision was inexplicable and had sympathy for the Watford players and manager, Aidy Boothroyd, who was sent to the stands after remonstrating with the officials.
Poll told BBC Radio 5 Live: "This is the most bizarre situation I've ever seen in 40 years watching football and 27 years refereeing.
"I heard about it then watched the highlights thinking 'it can't be how it's described', but it is. He (Bannister) has got a clear view of it. It's completely inexplicable.
"The referee must be respected, obviously, but in such circumstances, as a player, how do you not lose your temper?"
After the match, Boothroyd told BBC London 94.9: "I went to see the referee and in fairness to him, although he wasn't brilliant today, you can't blame him if there's a guy in his ear telling him it's a goal.
"The linesman has decided it's a goal. I've asked him about it and he said it was an optical illusion.
"I saw the ball go out for a goal-kick and my centre-half has put his hand up and asked for the goal-kick and for some strange reason a goal has been given."
Boothroyd rejected the idea that the Reading players should have allowed Watford to score following the error.
"I don't expect players to take things into their own hands. It's not up to them," he added.
"If someone stops you in a car park and gives you a present you don't say no do you?"
Watford's players confront the officials after the controversial goal
Coppell also played down the emphasis on the players to take action.
"The responsibility is not with the opposition to right a wrong. It is up to the officials to get it as right as they can," said Coppell.
Reading winger Stephen Hunt was bemused by the decision but tried to alleviate the blame from referee Attwell.
Hunt said: "It was a screamer! No, it was probably the worst decision I have ever witnessed.
"We can't do anything about it. It's not our mistake, but what can you do? You can't say 'no ref, it wasn't in'.
"He seemed all right. He's a young referee. But after this he'll probably be sitting at home next week.
"I've had him before and he's been all right. It was just a bad day at the office. He talks, he respects you and you respect him.
"I can understand Watford's frustration, but everyone makes mistakes."
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.