Slamming Arvind Kejriwal's one-year-old party for making "unrealistic promises" during assembly elections in Delhi, the leader of the opposition in Rajya Sabha said it should fulfil its "exaggerated and unimplementable" manifesto.

On his latest Facebook posting, Jaitley sought to know if the AAP is merely a "freak phenomenon" or will be a lasting experiment. He said no clear answers could be given at the moment.

"This party is unconventional. It has attempted to exploit the general mood of cynicism. It has made unrealistic promises and does not want to sit in a position of responsibility where it has to walk its talk," Jaitley said.

AAP's impressive performance in the Delhi elections came as a surprise to BJP and the Congress. It emerged as the second largest party with 28 seats in the 70-member assembly. BJP got 31 and its ally SAD won one seat. Congress with eight seats was a distant third.

"The very suggestion of being in the government to implement its policy and promises appears to be scary for this party. In a democracy, the voters vote in order to elect the government," Jaitley said.

Throwing a challenge to AAP and Congress, he said in the absence of clear majorities, forming a government is the art of the possible and Congress can extend its outside support to the AAP.

"In power, such a party (AAP) would be like a fish out of water. It is possible to make exaggerated promises, and capture the imagination of a few by making unimplementable promises. The strategy of the party is to avoid power rather than be in a position to implement the unimplementable," Jaitley said.