Congress chief Mallikarjun Kharge described Singh's resignation as "shutting the stable door after the horse has bolted". He further slammed PM Modi saying that he had forgotten that Manipur was a part of India.
The Congress on Sunday described N Biren Singh's resignation from the post of Manipur chief minister as "belated", and said "our frequent-flier" Prime Minister Narendra Modi must visit the state immediately and share with the people his plans to restore normalcy.
The opposition party's attack came shortly after Singh tendered his resignation to Governor Ajay Kumar Bhalla at the Raj Bhavan in Imphal.
Congress chief Mallikarjun Kharge described Singh's resignation as "shutting the stable door after the horse has bolted".
He also blamed Modi as the real culprit of "disdain and apathy" towards the strife-torn state.
"It is painful to say that for 21 months, the BJP ignited a fire in Manipur and left the people across communities to fend for themselves," Kharge said in a post on X.
"Their rank incompetence and utter disregard for Rajdharma resulted in at least 258 people having died, more than 5,600 arms and 6.5 lakh rounds of ammunition were looted from police armouries, more than 60,000 people displaced and thousands still forced to live in relief camps," he added.
Further slamming the prime minister, Kharge said Modi had forgotten that Manipur was a part of India. "It is high time he rejigs his memory and locate the state of Manipur on the map of India!"
"Modi ji has not stepped on Manipur's soil since his last election campaign in January 2022, although he had time to visit several foreign countries in between. Now that the chief minister has belatedly resigned, we hope and urge him to visit Manipur and hear the stories of horror from the people," the Congress chief added.
He expressed relief that better sense prevailed and that this was not a "2023-like-resignation-drama", referring to Singh's earlier offer to resign if it helped solve the conflict and bring normalcy.
Former Congress president Rahul Gandhi said Singh was forced to resign due to mounting public pressure, the Supreme Court's (SC) intervention and his party's plan to move a no-confidence motion in the assembly.
"For nearly two years, the BJP's Chief Minister Biren Singh instigated division in Manipur. Prime Minister Modi allowed him to continue despite the violence, loss of life, and the destruction of the idea of India in Manipur," the opposition leader in the Lok Sabha said in a post on X.
"The resignation of Chief Minister Biren Singh shows that mounting public pressure, the SC investigation and the no-confidence motion by the Congress have forced a reckoning," Gandhi added.
He, however, said the most urgent priority was to restore peace in the state and work to heal the wounds of the people.
"Prime Minister Narendra Modi must visit Manipur at once, listen to the people and finally explain his plan to bring back normalcy," he said.
AICC general secretary in-charge communications Jairam Ramesh said the Congress was all set to move a no-confidence motion against Singh and his council of ministers in the Manipur Assembly on Monday.
"Sensing the climate, the Manipur chief minister has just resigned. This was a demand that the Congress has been making since early May 2023, when Manipur erupted," he said in a post on X.
"The chief minister's resignation was belated. The people of Manipur now await a visit by our frequent-flier prime minister who is off to France and the US now -- and who has found neither the time nor the inclination to go to Manipur these past 20 months," Ramesh said.
AICC general secretary in-charge organisation KC Venugopal said it had been clear to the world since May 2023 that Singh's position as Manipur chief minister was untenable.
"It was also evident that he was unfit to remain in his post, yet the central government continued to shield him despite growing demands for his removal," he said in a post on X.
"For over 20 months, he fuelled chaos, exacerbating the civil war-like situation in Manipur. His inaction and active role in instigating violence cost many precious lives -- lives that could have been saved had he been removed earlier," he added.
Venugopal claimed that "the irrefutable audio clips exposing his role in inciting violence, and the Congress party's no-confidence motion against his government finally forced him to resign".
"We hope this marks the first step towards ending the horrific nightmare that Manipur has endured," he added.
Singh's resignation came hours after he returned from Delhi.
In a letter to the governor, he said, "It has been an honour to serve the people of Manipur thus far. I am extremely grateful to the central government for time actions, interventions, developmental work and implementation of various projects for safeguarding the interests of every single Manipuri."
"My sincere request to the central government through your good office is to continue with the same. I take the opportunity to enumerate the most important ones of them ... To maintain the territorial integrity of Manipur which has a rich and diverse civilisational history over thousands of years," he added.
Singh also requested the Centre to continue the "crackdown on border infiltration and to formulate policy for the deportation of the illegal immigrants and the fight against drugs and narco terrorism".
He urged the central government "to continue the stringent and fool-proof revised mechanism of Free Movement Regime with the biometric being stringently applied time bound and faster border which is underway".
On Saturday, Singh convened a meeting with BJP-led ruling alliance MLAs at the Secretariat. The meeting was held in the wake of the opposition Congress seeking to move a no-confidence motion against the government.
More than 250 people have been killed and thousands rendered homeless since ethnic violence broke out in the state in May 2023.