"One of their lady representatives has been now seen telling supporters that her community must cease to be secular and adopt a more communal approach.
"Such comments by a political party or its representatives cannot even be privately made. These comments reflect their mindset. They demonstrate that the alleged 'idealism' of AAP was put on one," Jaitley wrote on his blog.
"The mask has slipped, even if accidentally," he added, without naming the leader.
Jaitley's comments follow media reports about Ilmi, the Aam Aadmi Party candidate from Ghaziabad Lok Sabha seat, saying (in a video) that instead of being secular, Muslims should be communal.
He said that if the Delhi assembly election was the "high point" for the AAP, the Lok Sabha election would spell "doom" for it.
"AAP was a governance disaster in Delhi. It represented political adventurism. Its ideology was populist and only vote oriented," he said and added that the party demonstrated extreme opportunism.