Bale's two incredible performances against Inter Milan in the Champions League alerted a number of Europe's biggest clubs to the 21-year-old's potential while Modric has enjoyed his finest season at White Hart Lane to date, picking up the supporters' player of the year award after a series of impressive displays.
Manchester City, Barcelona and Manchester United have all been linked with big-money moves for the pair in the knowledge that they can offer either player the Champions League football that Spurs cannot.
Harry Redknapp has repeatedly stated his desire to keep all of his top players, and Levy supported the Tottenham manager's stance, saying in an open letter to supporters: "We have spent years and hundreds of millions of pounds investing in our first-team squad and in creating a settled team.
"Having quality players means they automatically attract attention from other clubs - but I can assure you that we have no reason to sell, and every intention of retaining, our key players. We shall simply not entertain any approaches for these players.''
Redknapp is also keen to move on at least 6 members of the first-team squad to make room for new signings and Kyle Walker and Kyle Naughton, who will return to White Hart Lane this summer after spending time on loan at Aston Villa and Leicester respectively.
Levy agrees with Redknapp and says the club will listen to offers for many of their players.
"We currently have one of the largest squads in the Premier League and, given the 25-man squad rule, it is no longer practical to retain players who are unlikely to qualify within that limit,'' the Spurs chairman said.
"We shall, therefore, look to reduce the number of these players during the coming summer transfer window in order to operate both effectively and efficiently.''
Spurs enjoyed a remarkable debut season in the Champions League this term, beating the two Milan giants before being knocked out by Real Madrid in the quarter-finals.
They have struggled in the league in the final third of the season and need a win against Birmingham to guarantee qualification to the Europa League.
Some Spurs fans feel disgruntled about the club's failure to make the top four but Levy insists they should be proud of the team's achievements this year.
"Harry and his coaching staff have worked with the squad to deliver performances during the season that fans will remember for years to come,'' Levy added. "This season we experienced our first venture in the Champions League and it was one which saw us reach the quarter-final stage.
"We achieved this playing some of the most entertaining and exciting football of the competition - truly memorable performances.
"We shall miss and all be disappointed at not qualifying for the Champions League for a subsequent year, but I know that the players will be fully focused next season on returning us to this elite competition.''