The Congress Legislative Party (CLP) in Karnataka on Sunday unanimously elected Siddaramaiah, 61, as its leader in Bangalore in presence of party general secretary and union Health Minister Ghulam Nabi Azad.
"By virtue of being the new CLP leader, Siddaramaiah will also be the opposition leader in the state legislative assembly," Azad, who is in charge of the party's Karnataka affairs, told the legislators, members and leaders who were present in full.
Chaos prevailed outside the party office on Queen's Road in downtown, as hundreds of Siddaramaiah's supporters blocked the main thoroughfare dancing, bursting fire crackers and whistling to celebrate their leader's election.
Even before the election proceedings were completed, Siddaramaiah's supporters laid a virtual siege on the party office causing unruly scenes and raising victory slogans.
Among the prominent leaders present at the CLP meeting were union Minister for Labour and Employment Mallikarjun Kharge, Law and Justice Minister M. Veerappa Moily and Minister of State for Railways K.H. Muniyappa.
External Affairs Minister and former state chief minister S.M. Krishna was conspicuously absent at the meeting as he was away in New Delhi.
The election was necessitated by the resignation of Kharge as CLP leader following his election to the Lok Sabha from Gulbarga constituency in north Karnataka and induction into the UPA government at the centre last month.
Azad said Siddaramaiah has a great responsibility to play an effective role as a CLP leader and guide the party's legislators in the legislative assembly in the right direction.
"As the leader of the opposition, Siddaramaiah has to check the corrupt elements and communal forces in the first BJP government in the southern state," Azad added.