Merson said he left Teesside partially because he wanted to escape an environment where he may be tempted to return to gambling and drinking. "I don't go around preaching to people to stop drinking and stop gambling, that's going to happen everywhere," he said. "They [the Middlesbrough players] are not gambling pounds 10,000 or pounds 20,000 but some of them like a bet and I can't just go into the dressing-room and tell them to stop."
The 30-year-old England midfielder, a recovering alcoholic who also has a history of gambling and drugs problems, added: "It goes much deeper than that, and I just had to get out of that environment. But I am not jumping off, anyone who says that is out of order. My conscience is clear. I went down from Arsenal to get them out of that division."
Robson was furious at Merson's comments. "This club has bent over backwards to help Paul Merson whenever he needed it. I am disappointed by his attitude and feel let down. The majority of my squad are near teetotallers and the players have not even had a card school for the away games in my five years at the club." He also refuted his former player's complaints that Boro lacked discipline and ambition.
Merson moved to Middlesbrough in July last year for pounds 4.5m after 13 years at Arsenal. Having made a recovery after years of personal problems, he earned an international recall, helped Boro win promotion to the Premier League and took part in the World Cup.
He was first reported to be considering leaving last week as his relationship with Paul Gascoigne, a fellow England player with a history of personal problems, reportedly deteriorated. It has been confirmed, however, that the Villa manager, John Gregory, had been approached by Merson's agent about his availability before the player made his potential health concerns public.
As Merson prepares to start a new chapter in his career - he was not signed in time to make his debut against Newcastle tonight - there seem to be more questions than answers over precisely why he has chosen now to move.
"There is a lot going on behind the scenes, things which I don't want to go into," he said. "I hope the fans don't get the hump because if they believe what they read, then they will think that I walked out."
He is adamant that there was no possibility of him moving to Tottenham. "I didn't ask to leave Middlesbrough. They let me go," Merson said.
"They tried to sell me to Tottenham, probably because there was the chance of a player swap. But I didn't want to go to Tottenham. If Aston Villa hadn't have come in for me, I would have stayed."
Merson becomes Villa's second most expensive player after the pounds 7m signing Stan Collymore and now there are doubts over whether he has a future at Villa Park. Gregory dropped a hint that Collymore's days may be numbered when he said: "I think our striker Julian Joachim needs someone of the experience of Paul Merson alongside him."
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