Washington: A new book claims that the Clinton Foundation received up to $5 million in donation from an Indian politician as the US debated a nuclear deal with India in 2008, tabloid New York Post reports.
The family of Hillary Clinton, who is making a bid to be US president in 2016, runs the foundation.
Amar Singh, then General Secretary of the Samajwadi Party and lawmaker, contributed between $1 million and $5 million to the Clinton Foundation in 2008, the Post cites the book "Clinton Cash" as saying.
The contribution, it reports, was made as the US Congress debated granting approval to the landmark India-US civil nuclear deal which Hillary Clinton, then a senator, eventually supported. The US Congress passed it with an overwhelming majority.
According to the book's author, Peter Schweizer, says the Post, the size of the donation, relative to Mr Singh's net worth, raised questions about whether he was the true source of the cash. It says the author speculates whether Mr Singh "was a conduit for other powerful interests in India pushing for approval of the nuke deal."
"Singh's donation was treated with suspicion and amusement in India," the paper says, noting that Mr Singh, had, in a financial disclosure at the time reported his total net worth as approximately $5 million.
"If true, that meant Singh had given between 20 and 100 percent of his entire net worth to the Clinton Foundation!" Mr Schweitzer is quoted as saying.
Ms Clinton had met Amar Singh in Washington in September 2008, the Post says. It describes Mr Singh as "a pal of Bill Clinton," Ms Clinton's husband and former US president.
Press Trust of India said calls in New Delhi to Amar Singh to seek his reaction went unanswered.
But both the Clinton Foundation and Ms Clinton's campaign have strongly refuted the suggestion of any wrongdoing and have maintained that there was transparency in receiving donations for the foundation's public cause.
"As the Foundation's impact has grown, so too has its commitment to transparency," Maura Pally from the Clinton Foundation said.