The North London club were left reeling after media reports in England stated that Kane wants to depart this summer.
Manchester City are the club showing the keenest interest in Kane, who will be with England at the European Championships this summer.
Gallas added exclusively to 888sport: "To be honest, Harry needs to leave Tottenham. He has to because they did not give him the opportunity to play in the Champions League next season.
"Harry is a world-class striker and top world-class strikers have to play in the Champions League.
"I know Harry wants to play in that competition and win trophies. When you have the talent like him you have to win trophies. For me, he has to leave.
"He played many years for Tottenham and did a great job but sometimes you have to be selfish. Fans of the club have to wish him all the best."
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