The 20-year-old concluded a reported £3m switch to the White Hart Lane outfit on Thursday after joining the Belgian club in the summer.
The former Red Devils youngster was due to join Spurs last summer but the north London side were unwilling to pay £6m compensation to the Premier League leaders.
The defender then joined Liege before André Villas-Boas snapped up Fryers this week, prompting Ferguson to criticise Tottenham’s transfer dealings.
“There’s nothing we can do about it but we should really register our discontent,” Ferguson told MUTV. “The registration should be stopped.
“To me, I think it’s a blatant manipulation of the rules. 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.”
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