Manchester United cannot do the quintuple. Who says so? None other than Sir Alex Ferguson, the United manager.

In a wide-ranging interview with his friend Alastair Campbell, the communications and strategy secretary to Tony Blair when he was Prime Minister, Ferguson says that a clean sweep of five trophies is “too tough a call”.

He also picks his Manchester United dream team — well, two, actually — and names Ryan Giggs as the player he would “never, ever leave out” of his best side. He admits that his biggest mistake was letting go of Jaap Stam, the Holland defender, and that his biggest regret was failing to sign Paul Gascoigne.

Ferguson believes that his present squad is the best he has managed, but although United have won the Club World Cup and Carling Cup and are favourites to retain the Barclays Premier League title despite last Saturday’s 4-1 home defeat by Liverpool, Ferguson fears that cup football’s unpredictable nature means that they could come unstuck in the FA Cup, in which they play Everton at Wembley in the semi-finals, or the Champions League, in which their quarter and possible semi-final opponents will be revealed tomorrow. “The thing about cup football is you need to be the best, but you also need a lot of luck, and I think it’s asking too much for all the games to go your way,” he said.

When asked by Campbell in today’s New Statesman to pick his best United XI, Ferguson, who took over at Old Trafford in 1986, says: “My problem is I have had so many great players that I can’t do one dream team.

“I ask myself who were the players you could not leave out. Roy Keane, Scholes, Giggs — [I would] never, ever leave him out if I was playing my best team. Ronaldo and Cantona are both ‘never leave out’ players. You’d have Beckham knocking on the door. As for Rooney, if I left him out, I’d have to do it by e-mail or I’d never hear the end of it. God, when you go through it like that, I have been blessed with terrific players.”

Ferguson’s relationship with Stam soured after the player published an autobiography, Head To Head, in which he revealed behind-the-scenes secrets from the United training ground. The former Holland centre back, who joined the club in 1998 and had been a mainstay of United’s 1999 treble-winning team, was sold to Lazio for £16.5 million. Although Ferguson was reported to have questioned Stam’s long-term fitness after Achilles tendon surgery, he went on to play at the highest level for several seasons. His departure left a hole in the United rearguard and it cost £30 million to fill, with the signing of Rio Ferdinand from Leeds United 11 months later.

Ferguson, 67, also discusses politics and the early experiences that have made him a lifelong supporter of the Labour Party, and names the players and managers that he admires.

He also reveals that he supports in principle the idea of a Great Britain side at the 2012 Olympic Games, although he is noncommittal about the prospect of managing it.

Furthermore, he mentions his eventual retirement — although Messrs Benítez, Wenger and others will be disappointed to learn that he is unwilling to name the date.

- TimesOnline