Sobhandeb Chattopadhyay, the Ballygunge MLA and the senior-most member of Bengal's 18th Legislative Assembly, has been named leader of Opposition, Trinamool sources said.

Dhanekhali MLA Asima Patra and Chowringhee MLA Nayana Bandyopadhyay will be the deputy leaders of Opposition.

With 80 MLAs in the new Assembly, Mamata Banerjee's Trinamool Congress, which ruled Bengal for 15 years, is the main opposition party in the state.

Former minister and Kolkata mayor Firhad Hakim has been appointed the chief whip.

Earlier on Saturday, Bengal’s first BJP government was sworn in with Suvendu Adhikari as chief minister in the presence of Prime Minister Modi at Kolkata's Brigade Parade Grounds.

Soon after, Mamata appealed to all opposition parties in Bengal to come together to form a "joint platform" to fight the BJP.

The BJP won 207 seats in the 294-member Assembly to form its first government in the state; the TMC won 80 seats.

"I call upon all opposition parties, including the Leftists and the ultra-Left, to come together to form a joint platform against the BJP," Banerjee said, also calling upon national parties to join.

"It is not the time to think the enemy's enemy is my friend, our first enemy is the BJP," she told a small gathering outside her Kalighat residence on the occasion of Rabindranath Tagore’s birth anniversary.

She alleged that TMC workers and supporters were facing attacks across the state after the announcement of the Assembly election results

"Hooliganism is going on at places, bad elements have entered their [BJP] ranks," she said.

The former chief minister claimed that no atrocities were allowed under her government after she came to power in 2011.