BJP vice-president Yashwant Sinha said that the note from the Bush administration to the Chairman of Foreign Relations Committee was not an ordinary communication. "It is a very, very important communication which sets out the policy of the administration, the government in the US," he said.

"The most important thing is that the communication is nine months old. Government of India must have been aware of it," he said.

Sinha said the government had claimed that India will retain the right to test. "We were assured of constant fuel supply. We will be benefited by sensitive nuclear technology."

The BJP leader claimed that as per the communication, the moment India tests nuclear device, all co-operation and all supplies to India will be stopped.

BJP spokesperson Rajiv Pratap Rudy said, "the shocking revelation made by Washington Post vindicates BJP's stand that the 123 Agreement would compulsorily prohibit any future tests by India, a fact which has been vehemently opposed by the Prime Minister, both inside and outside Parliament."

"Prime Minister Manmohan Singh has pulled a bluff on the nation and even deceived Parliament. The very fact that the contents of the letter were not revealed for nine months with a ploy that the PM gets over the crisis of nuclear deal in India is nothing but a blatant betrayal," he charged.

N-deal: UPA Govt thoroughly exposed, says Left

The CPM said its stand on the nuclear deal stood vindicated with the ‘disclosures’ by the US on the issue and asked the UPA government to suspend all further moves to operationalise the ‘anti-national’ agreement.

"The government should suspend all further moves to operationalise the anti-national nuclear deal," the CPM Politburo said in a statement.

Noting that the US has given ‘no binding fuel supply assurance’ to the country, the party said the Manmohan Singh government was ‘thoroughly exposed’ before the country for ‘compromising’ India's vital security interests.

"The Left parties had warned the UPA government about the provisions in the notes submitted to the UPA-Left Coordination Committee, which have now been vindicated by this disclosure. Each of the commitments made by the Prime Minister in Parliament have been violated," the statement said.

The CPM said proceeding with the nuclear deal will ‘mortgage’ India's sovereignty and make the country's civilian nuclear programme ‘vulnerable to US blackmail for the next 40 years.’

The CPM said the 26-page correspondence between US State Department and members of the American Congress has revealed that the US has given no binding fuel supply assurance to the country.