All five DMK ministers submited their resignation to Prime Minister Manmohan Singh on Wednesday.
MK Alagiri minister for chemicals and fertilizers and D Napoleon minister of state for social justice and empowerment put in their resignation.
S Jagathrakshakan, minister of state for information and broadcasting, S Gandhiselvan, minister of state for health and family welfare, and SS Palanimanickam, minister of state for finance, put in their papers after their party chief M Karunanidhi announced on Tuesday he was pulling out of the UPA to protest India's stand on Sri Lanka at the UNHRC.
After DMK pullout, speculation has mounted that the UPA will be vulnerable to pressures from its crucial outside supporters SP (22) and BSP (21) who together account for 43 seats.
BSP said it will continue to support the government from outside but will not join it.
"We will not be part of the government. We did not join it earlier and even now, we will not be part of it. We will continue to support it from outside," BSP supremo Mayawati told reporters outside Parliament House.
She said BSP was not supporting UPA for any benefit as was being alleged by some parties in NDA fold.
Samajwadi Party said that it will continue to support the UPA and final decision would be taken by supremo Mulayam Singh Yadav.
"It is true that there is upheaval at the Centre and counting of numbers has started to know whether the government would survive or not," Uttar Pradesh chief minister and SP state president Akhilesh Yadav told reporters.
"As far as support to the UPA is concerned, Netaji (Mulayam) will take the decision. Our entire central leadership is in Delhi and Lok Sabha is underway. Any decision would be taken in Lok Sabha and Netaji will finally decide," he said.
Earlier, the government insisted that it has not become "lame duck" after key ally's exit.
Finance minister P Chidambaram told a press conference in New Delhi on Wednesday that the government is "not aware" of the reason why the DMK chief changed his mind on supporting the government from the night of March 18 and the morning of March 19.
Unfazed by the DMK's withdrawal of support to the UPA, government on Wednesday asserted it was "absolutely stable" and not a "lame duck" and said it will move amendments to the resolution on Sri Lanka at UNHRC to send a "resolute message" on that country's human rights.
The government fielded three senior ministers -- P Chidambaram, Kamal Nath and Manish Tewari -- before the media to insist that DMK's demands were in the process of being considered and wondered why the ally changed its position after promising to reconsider its decision to withdraw support.
The UPA's second biggest constituent with 18 Lok Sabha MPs quit the alliance on Tuesday.
With questions being raised about the stability of the government, Kamal Nath, the minister for parliamentary affairs, firmly said, "We are not a lame duck government."
"The government is neither lame nor is it a duck. We are absolutely stable. No political party has come out to challenge our majority," he said.
Stating that India wanted the Geneva-based UN Human Rights Council to adopt a "strong" resolution on Sri Lanka, Chidambaram said India will move amendments to the draft to send a "resolute message" to that country on alleged human rights violations of Tamils and "goad" it to have an independent inquiry, a key demand of the DMK.
The finance minister also dismissed allegations that India had sought dilution of the strongly-worded resolution by the US, saying it was an absolute "canard".
He said DMK's other demand for a resolution to be adopted by Parliament on Sri Lankan Tamils issue was also in the process of consultations with other parties.
Chidambaram claimed that the DMK was aware of the government's position on the issue but had changed its position between the night of March 18 and morning of March 19.
"We are not aware of the reasons why the DMK changed its position between the night of March 18 and the morning of March 19," Chidambaram said, while noting that DMK supremo M Karunanidhi had said the party would reconsider decision to withdraw support if Parliament adopts a resolution before the end of current sittings on March 22.
At the same time, the three ministers asserted that there was no threat to the government despite DMK's pull out.
"Just because one ally pulled out, the government has not become weak... There is no political instability or political uncertainty... Nobody has questioned our stability except for few voices in the media," Chidambaram said.
Asked whether the government will test its stability by going in for Confidence Motion, the ministers rejected any such possibility.
"The question does not arise as we have the majority," Chidambaram said.
Rejecting the impression that the UPA is now weaker and "on more crutches", Chidambaram said, "We are in the government. It is our duty to steer the ship through the maelstorm and our hands are firmly on the wheel."
Reiterating that there should be "no doubt" about the government's stability or any "worry", Kamal Nath said it will continue with its policy decisions.
"We are absolutely, absolutely stable. If there is any test, it is on the floor of the House. But no political party has challenged the stability of the government," he said.
With the DMK pullout, the strength of the UPA in the Lok Sabha has been reduced to 224 but it enjoyed the support of 281 MPs that included those of outside supporting parties. The Lok Sabha has 539 MPs at present as four seats are vacant. The half-way mark is 27.
Asked whether the Congress would try to rope in some other parties, Nath said in politics, doors are always open.
Referring to DMK's demands, Chidambaram said the government had begun the process of formulating amendments to the draft resolution before the UNHRC.
"The amendments were finalised yesterday," he said, adding India's permanent representative to the UNHRC is in Delhi and he will be given "suitable instructions to move the amendments" at the UN meet.
He rejected reports that India was diluting the resolution, terming it as a "canard".
"India's position has always been and remains that the UNHRC should adopt a strong resolution that would send a resolute message to Sri Lanka and goad Sri Lanka to accept an independent and credible investigation," Chidambaram said.
On the fate of economic reforms and other welfare measures, Chidambaram said, "We will contine to push for legislation. Just yesterday, the Cabinet clerared the Food Security Bill.
"The bill will be introduced in Parliament and I am absolutely confident there will be enough support in Parliament to pass it," he said.
"As far as executive action is concerned, only this morning the ministers approved disinvestment in Sail. So we are taking executive actions, we are pushing bills. I dont' see us any weaker today than what we were yesterday.
Asked whether there was a possibility of a dialogue with DMK to persuade it to reconsider its decision, Nath said in democracy, doors are never shut.
On Samajwadi Party leader Ram Gopal Yadav's remarks that former Prime Minister Atal Bihari Vajpayee had better style of functioning, Nath said it was for him (Yadav) to say "if he finds BJP good or bad".
On DMK's other demand for Parliament's resolution, he said opinion was divided among political parties on whether there was a need for it as also the content.
Nath said he is holding consultations with other political parties in this regard to arrive at a consensus.
The three ministers insisted that the efforts for resolution were irrespective of whether DMK reconsiders its decision to withdraw support or not.
Chidambaram said the resolution was being contemplated keeping in view the sentiments of Tamil people.
"Every political party represents people. There are Tamils in the state of Tamil Nadu as also outside. There is also Tamil diaspora. Congress, from the time of Indira Gandhi and Rajiv Gandhi, has always stood for the rights of Tamils," he said.
In this regard, he referred to Congress President Sonia Gandhi's statement yesterday at CPP that reports of "unspeakable atrocities" on ethnic Tamils cannot go un-investigated and there must be "independent and credible" probe.
Nath said he had told political parties yesterday that the government wanted to bring the resolution keeping in view the sentiments of Tamils.
Here's how things unfolded:
SP to continue support, final decision to be taken by Mulayam: Akhilesh
BSP chief Mayawati says her party will continue outside support but not be part of it
MK Alagiri and D Napolean also submit too their resignations separately
Three DMK ministers submit their resignation to Prime Minister Manmohan Singh
Government says it is "absolutely stable" and not a "lame duck"