Radhakrishnan, a former Home minister, displayed the grenade, that has past its expiry date, during the budget discussion on grants for the home department.
He claimed that similar kind of stun grenade were used by police to disperse Youth Congress agitators in front of the secretariat last week.
Stun grenades are a type of non-lethal weapon used by security forces to disperse protesters by stunning them with its sound and flash.
"It is with these kind of arms, the government is facing Youth Congress agitators," he said.
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Seizing on the matter, senior CPI-M MLA S Sharma raised a point of order and said bringing arms to the House was not in order.
A senior legislator like Radhakrishnan should not have come with such a material, he said.
Intervening, Chief Minister Pinarayi Vijayan asked Radhakrishnan to place the grenade on the table of the House following which the legislator handed it over to the Speaker.