Rejecting the draft JPC report on 2G, Bharatiya Janata Party and Communist Party of India said it has been reduced to a "Congress report" and they will give their dissent notes separately.
They also alleged that it was a cover up exercise even as objections were raised on the leakage of the report.
"We shall reject it. We shall put forward our own views. It is a cover up story. It is a story done at the diktat of the Congress party," said CPI leader Gurudas Dasgupta.
Dasgupta, who is also a member of the JPC, said it is "absolutely contrary to the facts revealed".
He claimed a number of witnesses had showed that the prime minister was in the know of things and was even warned by one of his colleagues.
BJP spokesperson Meenakshi Lekhi said, "Since we were part of the JPC, we will submit our point of view which will become on record for all times in future and it will create history because these reports are there for posterity."
She justified the party's position taken at the time of demanding the JPC, saying "as a political party which believes in the system of governance, we cannot really overlook various system which are in place."
"But, after experiencing the misuse of the system, you could be wise in the hindsight. At the same time, the fact that you could be wise in parliamentary democracy, you believe in the Constitution and you believe in various systems, you expected the JPC members will rise above their position as Congress people.
"In fact, they will be people who are working for the country and see as statesmen more than as people of a political party. But that has not happened," said Lekhi.
CPI leader D Raja said, "It has become a Congress report" and his party would be preparing a dissent note as it did not agree with it.
He also criticised the leakage of the report, saying, "It is not at all acceptable to us. Still it is a draft report. The formal meeting of JPC is yet to take place. The report is yet to be formally adopted."
Raja also said "it is a clear attempt to cover up for the prime minister and the then finance minister."
The CPI leader also supported the then Telecome Minister A Raja's demand for deposing before the JPC, which was rejected by the JPC Chairman P C Chacko. The demand was also supported by BJP member Yashwant Sinha, who said his deposition before the JPC would help bring out the truth.
"On every occasion when the issue was raised in Parliament, the then telecom minister claimed that he took all the decisions with the knowledge of the prime minister in consultation with senior members of the Cabinet at that point of time. In such a situation, he should have been given an opportunity. He was not given an opportunity. The JPC did not discuss properly.
"What facts are available in public domain clearly show that JPC could not work objectively, impartially to fix the accountability. There is fault with the work of the JPC. There was fault in the functioning of the JPC Chairman," Raja said.
The JPC gave a clean chit to Prime Minister Manmohan Singh on 2G spectrum allocation, saying he was "misled" by the then Telecom Minister A Raja whose assurances stood "belied".
The draft report of the JPC also rubbishes the loss figure of Rs 1.76 lakh crore estimated by CAG, saying it was "ill-conceived".
The report, which was circulated among members before its adoption on April 25, also accuses Raja of forging the press note of January 7, 2008 after it was seen by the then Solicitor General G E Vahanvati.
"The committee wishes to point out that the procedure" regarding the First-Come-First-Served criteria was a "misrepresentation of facts and in tactic deviation from the existing procedure," it said.