"Suggestion by vested interests attempting to link it to the Indo-US Nuclear Deal is purely motivated mischief of those who first opposed the deal and are now its ardent supporters even at the altar of sacrificing liability provisions in case of nuclear accidents," party's communication department in- charge Randeep Surjewala told PTI.
The Congress leader was apparently targeting BJP, which had opposed the nuclear deal signed by the UPA-II dispensation.
"All contributions, if any, are in public domain under US law," he said.
Questions have been raised in a book whether the Clinton Foundation received money from Singh in 2008 in a quid pro quo arrangement for pushing the Indo-US nuclear deal.
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The book, 'Clinton Cash', speculated that Singh was the conduit for powerful interests in India which were pushing for the approval of the Indo-US nuclear deal, reported New York Post.
Hillary Clinton, who was the then Co-Chair of the Senate India Caucus and an eminent Senator, supported the bill, which was passed by the American Congress by an overwhelming majority.