On his return, they say Ronaldo is ready to leave Real Madrid after leading them to back-to-back Champions League titles.
Ronaldo (right) is the subject of a lawsuit brought by Spanish prosecutors over tax that they believe he should have paid on image rights income.
The report suggests Ronaldo told Fergie that he felt unloved at the club and has grown exhausted of his own fans booing him on certain occasions at a function before the Champions League final.
The 32-year-old Real Madrid striker, who is in Russian Federation as Portugal prepare for their Confederations Cup opener against Mexico, is said to be "outraged" after prosecutors accused him of defrauding the authorities of 14.7million euros (£12.8million).
Ronaldo has denied any wrongdoing Real officials said on Thursday that they were confident that he had acted legally.
The Portugal global, who is now away at the Confederations Cup, is understood to have informed the La Liga champions of his desire to leave during the transfer window in order to seek a fresh challenge. Aside from Manchester United and Barcelona, the next best team in the world would probably be Bayern Munich, managed by former Real Madrid head coach Carlo Ancelotti.
The Spanish prosecution in the indictment alleged that Ronaldo had evaded tax "in a conscious and voluntary manner".
"Very few clubs can meet his expectations".
43 - Ronaldo has scored three or more goals on 43 occasions in a match at club level, seven of those hat-tricks coming in the Champions League - a record he shares with Lionel Messi.