"The Prime Minister must come and explain. Today was his day in the Rajya Sabha and he was not present," CPI(M) leader Sitaram Yechury told reporters. The party also demanded registration of a case in the ''cash-for-vote'' scam.
In a statement, the party Polit Bureau said the report sent by US Charge d'Affaires Steven White should be the basis for filing an FIR and initiating an investigation against Satish Sharma and his aide Nachiketa Kapur, who were named in the diplomatic cable.
The WikiLeaks expose, published in The Hindu, confirmed what the Left parties had been saying in 2008 that MPs were bribed to vote in favour of the government, Yechury said.
"It is a humongous indictment of the Congress and the UPA government," he said and demanded an investigation into the matter by the CBI.
Yechury dubbed the revelations in the expose as an act of "gross moral degeneration and crass political opportunism" and undermined Indian democracy.
He wanted to know why investigation in the cash-for-votes scam did not continue. "Was it because it would have embarrased the government and the principal opposition," Yechury asked.
The CPI(M) leader was addressing a press conference which was attended by Gurudas Dasgupta and D Raja (CPI), former Prime Minister H D Devegowda (JDS), Nama Nageshwara Rao (TDP) and Shailendra Kumar (SP).
Dasgupta attacked Finance Minister Pranab Mukherjee's remarks in the Rajya Sabha that the matter of the 14th Lok Sabha could not be discussed in the current Lok Sabha.
"It is the same government that is in power, the same Prime Minister heads the government. Therefore it is the moral responsibility of the government to prove that they are clean," he said.
"It is not a legal question. It is a moral question and an ethical question," he said.
Dasgupta accused Mukherjee of concocting the argument by asking the opposition to move court on the matter.
"We shall not go to court. This is a matter for Parliament do decide. The judiciary does not run the country. The government runs it and the government has to answer," he said.
TDP''s Nama Nageshwara Rao said the UPA had committed a murder of democracy by buying votes for its survival.
"The UPA government has no authority to continue in office. The Prime Minister should come forward and make a statement. If he does not speak, he should resign," he said.