The party, however, defended Singh on the coal blocks allocation issue, saying he made the process more transparent and had even faced opposition from five non-Congress Chief Ministers.
"I do not want to comment as I have not gone through it . We will react after we study," party spokesman Randeep Surjewala told reporters when asked about the book "Crusader or Conspirator Coalgate and other Truths" which was released today.
Parakh has said in the book that "By continuing to head a government in which he had little political authority, his image has been seriously dented by 2G scam and coalgate although he has had a spotless record of personal integrity".
At the same time, the Congress spokesman recalled that the Prime Minister had indicated that the CBI lodging the FIR against Parakh in the coal block allocation was not proper.
On the issue of allocation, Surjewala claimed that the Prime Minister needed to be given credit for streamlining the process and making it transparent.
He said when the Prime Minister started to make the allocation process more transparent, five non-Congress Chief Ministers including those of Rajasthan, Chhattisgarh, Odisha, West Bengal and Jharkhand had opposed it.
Noting that the whole issue was now under the consideration of the Supreme Court, it would not be proper to say much in the matter.
Meanwhile, after the release of the book, Parakh claimed that the multi-crore coal block scam could have been avoided if the Prime Minister had used his authority in pushing reforms including open bidding of coal blocks.
If the Prime Minister used his authority of bringing in reforms including auction of coal block in open market and e-marketing of coal, there would have been no scam at all, he said.