The Left parties will submit by July 10 to President Pratibha Patil their letter withdrawing support to the UPA government, Forward Bloc general secretary Debabrata Biswas said on Monday.
The decision was unanimous, said Biswas.
The Left leader's comments came immediately after the government sent a letter to Left before the July 7 deadline expired.
The UPA government, in the letter, has expressed its wish to hold another round of meeting with the Left Parties to explain its position on the Indo-US nuclear deal.
Biswas, a Rajya Sabha member, told reporters "This is the unanimous decision of the four Left parties -- CPI(M), CPI, RSP and Forward Bloc.
"The Congress-led UPA Government is committed to the US on the 123 Agreement surrendering national interest and sovereignty. The decision to withdraw support is unchanged," he said.
Biswas who spoke to CPI(M) general secretary Prakash Karat over telephone during the day, said the decision of the withdrawal of support would be irrespective of the reply from External Affairs Minister Pranab Mukherjee to the letter of the Left parties.
He said, "Mukherjee might propose another meeting, but that will not change our decision."
Besides the issue of the nuclear deal, the letter would also highlight rising prices and inflation as the reasons for the withdrawal of the support.
He said the four Left Parties would meet on Tuesday to take stock of the situation and find a "political alternative".
The Left said they are in the process of finalising a comprehensive statement containing reasons and grounds for their withdrawal of support to the UPA government and will meet here tomorrow to discuss the entire gamut of political developments.
While confirming about the meeting on Tuesday evening, the statement, being characterised as a "chargesheet", will not center around only the nuclear issue. Instead it will give a detailed account of the government's failure to curb double digit inflation, mismanagement of economy and crisis in agriculture among the other things.
Talking to UNI, CPI leaders A B Bardhan and Shamim Faizi said, "The timing of the withdrawal will depend on the nature of the Congress reply to our clarifications when the government is approaching the IAEA."
The statement will also spell out how the government deviated from country's independent foreign policy and tilted towards the US, and how it voted against Iran in the IAEA and entered into an understanding with Israel with whom it carried out one billion dollar trade during 2006.
Basically it will be a critical review of deviation from the Common Minimum Programme (CMP) as well as other economic and social issues.
The CPI leaders, without naming Defence Minister A K Antony who has rejected the Left charge that the UPA was compromising India's foreign policy, said the traditional foreign policy enunciated by Pandit Jawaharlal Nehru had been given a go-by.
"It was based on not joining any bloc. The emphasis of the country's foreign policy was on NAM, with the focus on anti-imperalism and close relations with the developing countries, now "all these are being rejected by the present leadership of the Congress party."
On a media report that CPI(M) patriarch Jyoti Basu had asked party general secretary Prakash Karat to "go slow" over the pullout in view of party's likely big loss in West Bengal and Kerala in elections, a party senior functionary replied in the negative.
On Mr Antony's statement, Forward Bloc National Secretary G Devrajan said, "There is no use as the government has already been trapped by the US. It is so visible now."
With inputs from Agecnies