"That reflects we're doing things right at the club. It's a record and a pride," Bartomeu told Movistar following an eighth league crown in 11 years.
"Our main objective each season is La Liga. We'll have a very quiet celebration because Wednesday we have the challenge of the Champions.
"The objective is the treble. In the Champions League we will face a really strong rival and in the Copa del Rey our opponent is improving."
Bartomeu added: "This league is the result of all the players and coaches and the unconditional support of the fans.
"Levante played very well, it was a great victory in which we had to suffer until the last second because Levante looked for a draw till the death. The team and fans relaxed a little when it was 1-0."
Messi came off the bench to score the winner for champions Barca – his 10th La Liga title as he surpassed Andres Iniesta.
The Barca captain now has 33 league goals this season, 12 more than team-mate Luis Suarez and Real Madrid's Karim Benzema.
"He's the best in the world. When he comes onto the pitch, things happen," Bartomeu said. "He changed the atmosphere on the pitch, brought that magic... and scored another goal."