Mr Nath, while taking part in a discussion on 'vote of thanks' motion to the Governor's speech, told the Assembly that many BJP workers and supporters were murdered ahead of the February 18 Assembly elections in the state.
Police had recovered arms and weapons during a series of raids conducted by the police in the CPI(M) party offices, he claimed.
"Sarkar was exposed as the khalnayak of Tripura politics. His regime was reduced to mockery," Mr Nath said.
Manik Sarkar had served as the chief minister of Tripura for 20 years since 1998.
The CPI(M) had stashed weapons at its party offices to let loose terror on BJP and Indigenous People's Front of Tripura (IPFT) supporters, he said, adding that "absolute peace" now prevails in Tripura with the BJP at the helm of affairs.
In an oblique reference to CPM's allegations of post-poll violence, Ratan Lal Nath said the communist party has "planted" their supporters in the BJP and the IPFT to "create disturbances".
"People have given their mandate against the suffocating situation that prevailed during the last 25 years of communist rule," he said in the Assembly.
Former chief minister and Leader of the Opposition Manik Sarkar, on his part, said his party will provide "all round constructive cooperation" to the ruling BJP.
"We will cooperate with the government in a constructive manner and hope they would go for inclusive development," he said.
The former CM, however, stuck to his party's allegations of violence against the BJP in the aftermath of the elections.
There was a "concerted effort" to create unrest in the state's internal affairs, he said.
"Hundreds of our (CPM) party offices are being burnt down, attacked or captured. Our supporters have fled homes, many were physically injured " the Leader of the Opposition said.
He requested Chief Minister Biplab Kumar Deb to take stock of the situation and ensure that "peace is restored" in the state.
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