Mamata Banerjee and Trinamool Ballygunge MLA Sobhandeb Chattopadhyay on Monday approached Calcutta High Court challenging Speaker Rathindra Bose’s decision to recognise expelled legislator Ritabrata Banerjee as the leader of the Opposition in the Assembly.

The petition for urgent hearing, filed before Justice Krishna Rao, contends that an MLA expelled by the party cannot be recognised as leader of the Opposition. It also questions the validity of the Speaker’s interpretation of the Trinamool constitution and the status accorded to the rebel faction.

The matter will be heard at the top of the board on Thursday.

Although the party had formally nominated Chattopadhyay as leader of the Opposition, the Speaker recognised Ritabrata as the LoP after 58 of the 80 Trinamool MLAs extended their support to the expelled legislator.

During a recent trip to New Delhi, the Speaker told reporters that the expulsions of Ritabrata and another rebel MLA, Sandipan Saha, were not legally sustainable under the party’s constitution. Bose said this was why he had recognised Ritabrata as the LoP.

The petition filed by Chattopadhyay and Mamata in the high court seeks judicial scrutiny of the Speaker’s ruling and questions its legal basis.

With the first session of the 18th Assembly scheduled to begin on June 18, senior advocate Kishore Datta and former Bengal advocate-general Shirshanya Banerjee, appearing on behalf of Chattopadhyay and Mamata, sought an urgenthearing.

Justice Rao said the matter would be heard on June 11 and instructed the petitioners’ counsel to serve notices on all parties concerned. The petitioners’ side said the Speaker was the principal respondent inthe case.