The Lok Sabha on Monday witnessed a new low in MPs' behaviour with members of Janata Dal (United), Rashtriya Janata Dal almost coming to blows and exchanging unparliamentary epithets, and JD (U) member Prabhunath Singh, the man at the centre of the uproarious scenes, resigning his membership.

An obviously upset and angry Speaker Somnath Chatterjee described the incidents in the House as "condemnable" and warned that "strongest-possible action" would be taken if they were repeated. After an adjournment and when was peace was restored Lalu Prasad apologised for the bahaviour of RJD members but made it clear at the same time that no member or minister would remain a silent spectator if he was subjected to invectives.

In response, Prabhunath Singh, Lalu Prasad's political rival in Bihar, walked up to the Speaker and handed over his resignation. Outside he demanded action against Sadhu Yadav and challenged Lalu Prasad to contest elections against him in his constituency Maharajganj or Lalu's seat Chapra.

Singh, whose targeting of Congress President Sonia Gandhi [Images] and Railway Minister Lalu Prasad in the past had often created trouble in the House, again triggered the problem today when he attacked Lalu Prasad while referred to a rape case in Bihar during the zero hour proceedings. His remarks provoked adjournment of the proceedings by the Speaker and as the members were preparing for the break, Lalu Yadav's brother in law Sadhu Yadav, a backbencher, was seen menacingly approach Prabhunath Singh in the front rows in the middle.

Singh's NDA colleague, Braj Bhushan Singh, rushed and blocked Sadhu Yadav's progress. BJP member M A K Swain, who had also intervened to avoid trouble, earned the wrath of RJD member Rajendra Rana who threw a microphone at him.

It failed to hit the target because it was wired. Singh's remarks infuriated Lalu Prasad, who was heard trading charges, and his party members who rushed to the front benches.

As the House reassembled, the Speaker said the incident had brought a bad name to the Parliament. "Our very existence is for this institution. Let us not destroy it."

After Lalu's apology, Prabhunath Singh contended that he had not insulted anyone but said action should be taken against him if he was found guilty. He also said he was not fit to be in the House and walked to the Speaker, gave his resignation and left the House.

Swain said after nine years in the Lok Sabha he was frightened on Thursday after the incident. "Should I come to the House with my bodyguard?" he asked the Speaker.

"You will be fully protected," Chatterjee told the BJP member adding that all the members had the right to be fully protected. Earlier, the Speaker's attempt to bring peace with an adjournment failed to work when the members trade charges and the House was adjourned against till 2.00 pm.