In a statement following the Sunday firebombing of the Rivers House of Assembly, Clark issued the warning.
He claimed that the strategy to topple Fubara and destabilize Rivers was what led to the fire catastrophe.
When the elder statesman went to the assembly facility to evaluate the extent of damage following the incident, he said that Fubara was subjected to tear gas and even threatened with gunfire.
"The reported events in Rivers during the past 24 hours have really upset me.
"I am aware that the goal is to remove the governor, compel Prof. Ngozi Odu, his deputy, to step down, and install the Speaker of the House of Assembly in his place.
"Let me say this with conviction: we won't let that happen!
Clark charged, "The consequences would be dire for the national economy and the stability of the region."
He observed that the people of Rivers had experienced enough political upheavals.
He said, "The state and the Niger Delta Region by extension should not be allowed to regress into their dark past."
In order to prevent any such crises in the state, the elder statesman urged President Bola Tinubu to give security agencies in Rivers direction.
In the best interests of his government and the country's democracy, he pleaded with the president to move quickly to stop the catastrophe that was rapidly developing in Rivers.
Additionally, Clark cautioned that special interests shouldn't be let to act as they want, pointing out that Nigeria is a democracy and that everyone should respect the principles of constitutional democracy.