Trouble broke out when AIFB member Tajmul Hossain after the Question Hour session sought adjournment of the House and the Speaker's permission to read out a motion in this regard.
Although the Speaker allowed him to read it out initially, pandemonium broke out as his mike was switched off and both LF and Trinamool MLAs started shouting against each other.
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Shortly afterwards, LF MLAs staged a walk out from the House.
Congress members continued their boycott of the Assembly.
Later, Forward Bloc member Paresh Adhikary told reporters that De, an ex-minister, and Patra had been attacked by TMC-backed activists and demanded immediate arrest of the culprits.
De received severe injuries in his eyes and he would have to be shifted to a city hospital, he added.