"Let me tell the people from this House that we will be contesting the assembly polls next year under the leadership of Nitish Kumar," he said.
The deputy chief minister, who also holds the finance portfolio, was replying to a debate on the appropriation bill when he made the statement in presence of the chief minister.
The NDA in Bihar comprises Kumar's JD(U), Union minister Ram Vilas Paswan's LJP and the BJP. The coalition had won 39 out of the 40 Lok Sabha seats in the state.
Sushil Modi's remarks came in the backdrop of the BJP issuing a show cause notice to its MLC Sachidananda Rai, who had last week launched a vitriolic attack against Kumar.
He had hit out at Kumar after media reports claimed that the special branch of state police had issued a missive two months ago seeking details of district-level functionaries of the RSS and its affiliates.
The remarks drew strong criticism from JD(U) leader Pavan Varma, who on Sunday, said this kind of behaviour cannot be adopted in an alliance government and dared the BJP to fight the elections alone.
The saffron party had fought the 2015 assembly polls without Nitish Kumar by its side. Despite having allies like the LJP in addition to Upendra Kushwaha's RLSP and Jitan Ram Manjhi's HAM, the NDA was trounced in the elections.
Kumar, in alliance with the RJD and the Congress, had returned to power with a thumping majority.
Corruption scandals involving his then deputy and RJD leader Tejashwi Yadav led to Kumar's exit from the Grand Alliance and his return to the NDA in 2017.
Sushil Modi also mocked leaders of the Congress-RJD combine who have been predicting the break-up of the BJP-JD(U) alliance following developments like the police department's missive and Kumar's reluctance to have his representatives in the Union council of ministers.
The opposition coalition has also been urging Kumar to switch sides and provide leadership to anti-NDA forces.
"Let there be no illusions. Nobody rides a sinking boat. And this boat is full of holes which bagged only one seat in the Lok Sabha polls," Sushil Modi said referring to the opposition 'Mahagathbandhan' which comprises five parties.
"The 15 years of misrule of the RJD-Congress made us begin from scratch when we first came to power in 2005. They complain that we keep referring to their tenure. Had you provided the state with a strong foundation, we would have got some help in erecting the structure of development. But they left Bihar looking like a shamshan ghat (cremation ground)," he said.
He said let the people of the state weigh their 15 years in power against the NDA's regime in the assembly polls next year. The deputy chief minister also took exception to the prolonged absence of Tejashwi Yadav, who is the leader of the opposition, from the House.
"It is the 17th day of the ongoing session and not once has he taken part in any debate. It must be the first instance of its kind in the history of this assembly," he said.
Turning to Speaker Vijay Kumar Chaudhary, the Sushil Modi wondered whether Yadav was even aware of the rules applicable on members of the House.
"Has he even sought your permission before remaining absent. What is the reason for his absence, none of us know," he said.
Yadav has appeared in public just a few times after the Lok Sabha poll results. He has claimed that he has been convalescing after undergoing a surgery for a ligament injury.
However, it is widely believed that the younger son of RJD chief Lalu Prasad is upset over his elder brother Tej Pratap Yadav refusing to tow the party line in the absence of their father, who is serving prison sentences in fodder scam cases.