The 20-year old defender departed Old Trafford for Standard Liege last summer but has now been snapped up by Spurs who were in pursuit of him when his United contract was expiring.
Tottenham did not want to pay the transfer fee and compensation package so waited for him to leave United before bringing him in from Belgium much to the disappointment of Ferguson.
"To me, I think it's a blatant manipulation of the rules,” he told MUTV.
"Tottenham did nothing wrong as he went to Standard Liege. They tried to buy him off us and we'd been looking for a certain figure. They wouldn't pay it but asked if they could take him down there on trial and, at that time, he was out of contract in June anyway.
"So he went down on trial and he went to Portugal with them. They then said they weren't prepared to pay the money and, all of a sudden, he signed for Standard Liege.
"We knew immediately and suspected that he would return to Tottenham in January and that's happened. It's a [Spurs chairman] Daniel Levy deal. You know, it's his fingerprints all over it. It's the kind of thing we expected he was going to do."