Paul Scholes has warned Alex Ferguson's Premiership rivals not to expect an imminent retirement from the Manchester United manager.

Ferguson celebrates an incredible 20 years in the Red Devils hot-seat on Monday, when the great and the good of English football will gather in the north-west for a lunch in his honour.

Tributes to Ferguson have been flowing into United from all quarters of the globe, with even Arsene Wenger admitting he will be sad when his old adversary eventually decides to step away from the game.

Yet, according to Scholes, who has spent his entire club career working under Ferguson, that day is not anticipated any time soon.

The United midfielder is not prone to exaggeration so when he suggests Ferguson retains the same hunger and desire he has always had, the chances are it is true.

"Who knows how long he will go on," reflected Scholes.

"He is not looking any older and he still enjoys coming out on the training ground every day. He loves it, even in the freezing cold, so I think he will be around for a while yet.

"The thing is, you can't imagine life at United without him. One day it will happen, we are all aware of that, and when it does it will be a great shame because of what he has achieved here.

"When a new manager takes over, there will certainly be a big void to fill. But, as I say, I don't believe that day will come soon because he is still desperate to win trophies, whether it is the cup or league."

After spending the best part of 14 years working with Ferguson, along with team-mates Gary Neville and Ryan Giggs, Scholes as a unique insight into what drives the most successful manager Britain has ever produced.

As a kid, learning his way in the game, Scholes was drawn into the popular belief Ferguson's powers were based around his notoriously fiery temper.

The former England international now knows that is not the case, although the fear factor has not disappeared.

"When I first met him I was frightened, frightened to death actually. I still am," he said. "When you are a kid you hear about the fiery side of him and when you meet him that is all you think about.

"He has definitely mellowed since those early days but if he is not happy about something, he will still let you know. I have not had a 'hair dryer' for a while, but that means there is probably one just around the corner."