The Welshman is the most expensive player ever sold by a British club, with Spurs having shipped him out to Los Blancos in 2013 for a world record £86m fee.
Bale starred for Real in his debut season and helped the Spaniards to land their 10th European Cup – he netted in the final against Atletico Madrid – but his relationship with the club and talismanic team-mate Cristiano Ronaldo has recently turned sour.
Sections of the La Liga giants’ supporters have been critical of the winger’s performances, while the reigning Ballon d’Or holder reacted angrily when his attacking partner turned the ball home after his initial shot was saved.
United are understood to have made Bale a top target heading into the summer as they plan a big money first-team overhaul, but Chelsea are plotting to win the race.
Reports claim that a £72.3m sum is in place for the player and that the London club are willing to pay him £300,000-per-week to return to the Premier League.