Speaker G Karthikeyan adjourned the house for the day ahead of schedule after rushing through the business following slogan shouting by LDF members who demanded arrest of Basheer, an MLA from Ernad segment in Malappuram.
IUML is a major constituent of the ruling Congress-led UDF.
CPI-M deputy leader in the house Kodiyeri Balakrishnan raised an adjournment motion to take up the issue of murder of two brothers by a gang at Kuni in Malappuram district on Sunday last.
He said the two, accused in a case connected with IUML activist Atheeq Rehman's murder, were killed brutally and that it had taken place a few days after MLA Basheer 'threatened' the victims during a public meeting.
Balakrishnan alleged that the government was protecting the ruling Front MLA.
Replying to the notice for the motion, both Chief Minister Oommen Chandy and Home Minister Thiruvanchoor Radhakrishnan said the government would not protect the guilty and that a probe would be held "without any political interference".
Radhakrishnan said an impartial probe would be held into the murder and pointed out that a Special Investigation Team has been set up for the purpose. "A case had been registered with 11 persons as accused", he said.
On LDF's demand for Basheer's arrest, Chandy said it could not be done just because his name had been included in the FIR. After the police probe, steps would be taken as per law, he said, adding, the charge against Basheer was that he had incited people to take revenge.
The brothers were attacked by a seven-member gang while they were sitting in front of their shops on Sunday night.
Announcing LDF decision's to boycott the proceedings, Opposition leader V S Achuthanandan alleged that the Chief Minister and Home Minister were protecting the MLA. "This is a disgrace to the Kerala assembly which has a rich tradition", he said.