Both Barcelona and Real Madrid have been linked to the 22-year-old Portugal international whose dazzling form has helped United's push towards prising the Premiership title away from Chelsea.

Charlton told BBC Radio on Monday: "They link themselves to whoever they feel fit and it's not right.

"I don't think it's a correct way to go about their business."

Charlton is confident Ronaldo will reject the overtures from Spain and sign an extension to his existing contract which would keep him at Old Trafford until 2012.

"I can see no reason at all why he should want to play for another club.

"It's really destabilising for both the club and the player to have all this speculation about his future. All of it is coming from abroad and none from our club."

Ronaldo -- who had seemed to be on his way out of the club following adverse headlines after teammate Wayne Rooney's sending-off in the World Cup quarterfinal between Portugal and England -- confirmed last month that he was ready to thrash out a new deal with United.