Bale has been linked with the likes of Barcelona, Real Madrid, Inter and Manchester United after his impressive performances over the last year, but Spurs have always been adamant that they are not interested in listening to offers.
Having seen his hugely promising West Ham squad broken up following the sale of Rio Ferdinand to Leeds in 2000, he is determined that Spurs will avoid that fate.
"We couldn't look to sell him," he said. "You start selling him and it sends out the wrong signals. For me it would be like when West Ham sold Rio at that time.
"They think, 'Well, the club's not got any real ambition, we're not going anywhere', and I think that would happen with Gareth. We've got to keep him here as long as we possibly can and really build the team around him. It's those people you've got to keep."
Redknapp had sought to add a striker to the squad in January, with Andy Carroll and Giuseppe Rossi among those Spurs expressed an interest in signing, but the manager is hopeful Jermain Defoe, Peter Crouch and Roman Pavlyuchenko can deliver in the second half of the season.
"They are our strikeforce now," he said. "We are relying on those three to produce the goals. Van der Vaart is the only man who has got his ratio of goals. We need the strikers to start scoring regularly as well."
Defoe has yet to score in the league this season and Redknapp added: "We are waiting for him to suddenly have that burst of goals that could make the difference to us.
"If he can go on a run and score some goals he can take us where we want to go. We are relying on him. He is a fantastic finisher.
''Goalscorers need confidence. The other night he had a couple of one on ones that he would normally score (but) once they do start going in for him he will start going on a run."