"We have asked for a thorough enquiry on the coal block allocation. Everybody involved should be brought to book and punished. And more importantly what is been lost must be sought to be recovered," Yechury told media here.
"In the parliament, we have pressurized the prime minister, who held the coal portfolio, to come and made a statement, he made a statement very reluctantly," he said.
"We were not satisfied of his statement but at least we could get assurance from him that his government will cooperate fully with the investigation being done by CBI under the supervision of Supreme Court," he added.
Yechury further said: "We want the investigation to be completed as soon as possible without any fear by the CBI and without under any pressure, we want the Supreme Court to properly supervise and monitor this investigation."
The Prime Minister's Office (PMO) has defended the coal block allocation made to Hindalco terming it as entirely appropriate.
In a statement issued on Saturday, the PMO said the decision was based on the merits of the case placed before him by the coal ministry with a strong recommendation of the Odisha Government.
Tracing the procedures followed before the allocation was made, it said the Prime Minister was satisfied over the final decision taken in the case.
The statement said the allocation is subjected to an on going investigation and no impediment is placed before the CBI to continue the investigation and seek fresh information, which may have a bearing in the case.
The statement said the investigation on this and other matters must take their normal course under the law.
The CBI has lodged an FIR against industrialist Kumar Mangalam Birla, and former Coal Secretary P.C. Parakh as part of its ongoing probe in the coal blocks allocation case.
Union Commerce and Industry Minister Anand Sharma had earlier come out in support of Birla, and urged the government agencies to not play to the gallery and create an environment of sensation and shock.
The Commerce and Industry Minister's support for Birla came a day after the CBI filed an FIR against him in the coal blocks allotment scandal.
The BJP has held the Prime Minister responsible and demanded his resignation for an estimated loss of Rs 1.86 lakh crores to the national exchequer by the CAG in connection with the coal block allocation.
The CAG report does not indict the Prime Minister or his office, but the BJP is emphasizing that the Prime Minister held direct charge of the coal ministry for the years under scrutiny.
--ANI (Posted on 20-10-2013)