Speaking a day after she announced the dramatic decision, Trinamool Congress leader and West Bengal Chief Minister Mamata Banerjee launched a scathing attack on the Congress, which heads the UPA.
"We will not budge from our stand no matter what... Our ministers will resign as stated," she told the media at Writers's Building in Kolkata.
She rubbished Finance Minister P. Chidambaram's claim that the Congress had tried to reach her on the issue of reforms to stop her threatened exit from the United Progressive Alliance.
"I must make it clear that there has been no effort from the Congress to reach me. A section of TV channels is spreading misinformation."
With Trinamool's ministers in the Manmohan Singh government set to resign Friday, the Congress was at its diplomatic best vis-a-vis Banerjee but insisted that the big ticket reforms were here to stay.
"These decisions were taken after the most careful consideration… They stand," Chidambaram said.
These include allowing foreign direct investment (FDI) in multi-brand retail, hike in diesel prices and a cap of six subsidised cooking gas cylinders per family - which forced the Trinamool to dump the UPA.
With the Trinamool's 19 members leaving, the UPA has lost its effective working majority in the 545-seat Lok Sabha.
But Information and Broadcasting Minister Ambika Soni said: "The UPA government is not in any danger."
She said the UPA government had always managed its numbers when tough decisions were needed to be taken.
One Trinamool MP, Kunal Ghosh, Wednesday demanded that Prime Minister Manmohan Singh should himself quit.
"Before accepting the resignation of our ministers, the PM should step down and go for a fresh mandate on whether the country (wants his) policies or not."
The Trinamool's belligerence came a day ahead of a nationwide strike called by the opposition to protest against last week's government reforms aimed at kickstarting a flagging economy.
The strike also has the support of the DMK, a UPA ally.
The Left Wednesday asked the government to roll back its decisions on FDI, diesel and cooking gas cylinders -- or quit.
"FDI in multi-brand retail trade is opposed by the majority in parliament," Communist Party of India-Marxist leader Prakash Karat said in New Delhi.
"So the government should not proceed with this. Nor should it proceed with the increase in diesel prices or limitation in gas cylinders.
"If the government does not roll back these measures, it has no right to continue in office," he added.
Both Agriculture Minister and NCP leader Sharad Pawar and RJD's Lalu Prasad were confident that the UPA will tide over the crisis.
The Trinamool decision has made the Congress more dependent on the Samajwadi Party and the Bahujan Samaj Party (BSP).
On Wednesday, Samajwadi chief Mulayam Singh Yadav warned that the "arrogance" of the Congress was going to hurt it badly.
The Congress, meanwhile, said that consumers in Congress-ruled states will get three more cooking gas cylinders at subsidized rates.
A subsidised cooking gas cylinder costs Rs.399, compared to the market price of Rs.750.
Mamata Banerjee made fun of this.
Calling the cap on subsidised LPG cylinders at six amounted to asking people to starve ("dieting, not eating"), she demanded that the cap should go up to at least 24 cylinders a year.