All six Trinamool Congress ministers Friday resigned from the government and the party withdrew support to the UPA, three days after it said it was quitting the alliance over economic reforms.
Railway Minister Mukul Roy and five ministers of state called on the prime minister and submitted separate resignation letters. The meeting barely lasted five minutes.
Trinamool leader Sudip Bandopadhyay, who was the minister of state for health, quoted the prime minister as saying that he was "sad" the Trinamool was leaving the Congress-led government.
From the prime minister's residence, the ministers drove to Rashtrapati Bhavan and handed over to President Pranab Mukherjee a letter ending the party's support to the UPA government.
The Trinamool has 19 members in the 545-seat Lok Sabha.
Saugata Roy, the minister of state for urban development in the UPA government, told reporters at the forecourt of Rastrapati Bhavan that the letter of withdrawal of support to UPA was signed by Mukul Roy.
"We thank both of them (prime minister and president) for accepting our letters," Saugata Roy said.
Asked what Manmohan Singh told them, he said: "What the prime minister had said or not said to us is confidential information between the prime minister and the just resigned ministers."
Banerjee had Tuesday said her ministers would leave the United Progressive Alliance (UPA) government unless it reversed its decisions on capping cooking gas cylinders, allowing FDI in multi-brand retail and hiking diesel rates.
The exit of Trinamool from the UPA government comes after nearly two years of troubles in their relationship.
The government has said that the fresh set of economic polices were vital to kickstart a sagging economy. The Trinamool says these policies would cause widespread ruin.