Chelsea are understood to have had a £22million offer for the Croatian playmaker rejected on Wednesday, with Redknapp keen to hold on to the 25-year-old, who enjoyed a superb season at the heart of the Spurs midfield last year.
The 64-year-old recently described Modric as "irreplaceable" in the wake of reported interest from the Blues and has hit out at the Londoners' offer. Redknapp told the BBC: "Luka is not for sale. If there has been a bid of £22m that is ridiculous. There are people being sold for £20m who are not fit to lace Luka's boots."
Modric may have scored just four goals last season, but his tireless performances and creativity make him an obvious target for any top team looking to improve their midfield.
Earlier this month Modric told a Croatian newspaper that he was happy at Spurs but would be open to a move if the club altered their stance and chose to sell him.
"If an offer comes which is good for Tottenham and for me also, then a transfer is possible," said Modric, who signed a new contract last year.
Redknapp reacted angrily to suggestions Modric could leave by insisting that the club's progression depended on retaining the services of players like him and star winger Gareth Bale.
Manchester United, who have a vacancy in midfield following the retirement of Paul Scholes, have also been linked with Modric, but Chelsea are thought to be the only team to have made a bid to sign the star so far.
Both Chelsea and United could offer the Champions League that Spurs cannot after they only finished fifth last season, qualifying them for the Europa League.
Source: PA
Source: PA