Arvind Kejriwal was Monday elected the leader of the legislature party of the Aam Aadmi Party (AAP).
The legislature party meeting was held at the Constitutional Club and attended by all the 28 newly-elected MLAs.
Kejriwal later told reporters that his party was prepared to play the role of a "constructive opposition".
"Why is BJP running away from responsibility? It should make the government. They got the maximum seats. They can make an alliance with the Congress and form the government," he said.
He also expressed his complete support to Anna Hazare's agitation demanding Janlokpal Bill which will begin Tuesday.
In the meeting, he asked all his 28 legislators to launch a door-to-door campaign starting Tuesday to thank people for leading them to victory in the assembly elections.
Earlier, in the party's core group meeting held at Kejriwal's residence, he asked all winning candidates to report if any party approaches them to seek their support.
Sources said the AAP chief was suspicious of horse-trading and was making best efforts to keep the newly-elected flock intact and united.
The debutant political party emerged as the second largest party in the Delhi assembly elections with 28 seats after the BJP, which won 31 seats. Both of them lack the absolute majority (36 seats) figure needed to form the government.