Croatia midfielder Modric has been in scintillating form for Spurs this season, playing a key role in their run to the Champions League quarter-finals on their debut in the competition.
The 25-year-old has been linked with a host of rival clubs, including Chelsea, Juventus and Inter Milan, but Redknapp told Croatian newspaper Sportske Novosti: "I wouldn't want to sell him for ?£100million, not even for a billion. He's the hub of the team."
Modric signed a new six-year contract contract with Tottenham last summer and his agent Mario Mamic dismissed speculation about a move away.
"These are just rumours," he told Calcio Mercato. "Luka has a contract until 2016 and Tottenham have no plans to sell him.
"He has an excellent relationship with the coach, Redknapp, and only signed a contract extension with Spurs last summer."
Modric is one of a quartet of Croatia internationals currently on Spurs' books but he could be the only one left next season.
Midfielder Niko Kranjcar has already confirmed he would look to quit the club in search of regular football, while there is also doubt over the future of right-back Vedran Corluka.
Redknapp said: "Niko's a great player and a great guy, very polite, but the guy just has no luck.
"I don't want him to leave the club - he was fantastic last season - but we've got Gareth Bale out on the left of midfield."
Source: PA
Source: PA