Spurs sit seven points behind fourth-placed Manchester City and the Belgian defender accepts his side have struggled to better the standards they set last term
Spurs spent heavily in the close-season to bring the likes of Erik Lamela, Christian Eriksen and Paulinho to White Hart Lane, but they trail fourth-placed Manchester City by seven points with just eight games remaining in their Premier League season.
Furthermore, Manuel Pellegrini's men have three games in hand, and rank highly among the title favourites.
And centre-back Vertonghen concedes Tottenham have failed to improve on last season's standards, but retains belief that the current squad can qualify for Europe's premier competition next term.
"I do not want to look at the table anymore because the gap [to the top four] is very big," he said.
"All four sides at the top are stronger than they were last year and we have stayed at the same level. If you see last season, then we did not improve.
"I think we do have the players to achieve Champions League [qualification] and I hope we can achieve it next year."