"It (Reliance) has got the maximum number of oil vouchers. It has paid the maximum surcharge. But no investigation has been carried out against it. I fail to understand why," CPI(M) general secretary Prakash Karat told reporters here.

He said that Reliance was one of the four parties named by the UN-sponsored Volcker committee, which went into Iraq's oil for food scam during Saddam Hussain's regime, and the firm was the biggest beneficiary.

"We will demand in Parliament that investigations should be carried out against Reliance," the CPI(M) General secretary said.

As per the terms of reference of Justice R S Pathak committee, the probe was limited to the role of Natwar Singh and Congress, Karat said hinting that other beneficiaries including Reliance were outside the purview of the investigation.

"I do not understand why no investigation is being carried out against the oil company", Karat said. "Even the Congress and the BJP are both silent on the issue".

It is established that another named beneficiary Bhim Singh of Panthers Party, who got the oil vouchers, did not use them, he said.

Expressing displeasure on the manner in which the Pathak committee report was leaked to the media when Parliament session was going on, he said "those responsible for the leakage should be punished".