Bale's appearance at their kit launch in London followed reports last week that Real Madrid had conceded defeat in their battle to sign him.
His Tottenham team-mate Defoe said: "It's important that he stays.
"This year we want a great season and we want to get into the Champions League - and to do that you've got to keep your best players.
"What Gareth did here last year was unbelievable when you look at the amount of goals he scored.
"At times he was playing out of position, up top or off the forward. And to show the composure he did in certain games when he was one-on-one with the keeper and produced some unbelievable finishes. He's a special player."