If Bale were to move to Inter Milan for the reported fee, he would be the most expensive British player in history, breaking the record set by Rio Ferdinand's £29m move from Leeds to Manchester United in 2002.
However, Redknapp said he wanted to keep hold of the "special players" in his team, who are looking to build upon this season's first appearance in the Champions League.
"You've got three or four players who can make a difference and he's one of those players," added Redknapp
"And, if you lose him, you can't replace him. Where are you going to replace him?
"When he gets the ball something happens, he can do something that no-one else can do. We can't afford to lose him."
Bale has previously publicly expressed his desire to stay at White Hart Lane, telling BBC Sport in November that "I want to keep playing at Tottenham and keep enjoying my football."
And in December, Tottenham chairman Daniel Levy said: "Gareth has got a long contract and I can assure you he will not be sold."
Tom Huddlestone's had a setback and it seems he's going to be out longer than we expected
Spurs boss Harry Redknapp
While Bale's long-term future is under scrutiny, Redknapp has short-term problems in the shape of an injury to key midfielder Tom Huddlestone, who has been battling with an ankle problem since November.
Redknapp is worried that he may need to leave Huddlestone out of the club's 25-man squad for the Premier League.
"Tom's had a setback and it seems he's going to be longer than we expected," Redknapp said.
"His ankle is sore. He tried to do a bit of running and is still a long way away.
"We will have to look at his situation with regard to the 25-man squad. I am hoping he'll be OK as he is important to us and is a fantastic player.
"We need him but we will have to make sure how it goes and discuss it with the medical people."
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