Michael Pillsbury, an informal White House adviser on China, said he received information about the business activities of Hunter Biden during a visit to Beijing in the same week Donald Trump urged China to probe the son of Joe Biden.
Speaking to Fox Business on Wednesday, Mr Pillsbury said he had raised the issue of the Bidens during a visit to China a week ago.
“I tried to bring up the topic in Beijing,” Mr Pillsbury said. “I’ve never seen them get so secretive in my entire life. They would discuss ICBM warheads sooner than talk about what Hunter Biden was doing in China with [former] vice-president Biden.”
Mr Trump came under heavy fire last week after publicly urging China to investigate the Bidens in a move that mirrored his request to the Ukraine’s president in a July phone call that has sparked an impeachment inquiry.
Following his appearance on Fox Business, Mr Pillsbury said he had actually been successful in obtaining information from his Chinese contacts about Hunter Biden.
“I got a quite a bit of background on Hunter Biden from the Chinese,” Mr Pillsbury told the Financial Times.
Mr Pillsbury, a China hawk who was widely seen as far from the mainstream before the Trump administration came to power, shares a similar stance on China to Peter Navarro, a trade adviser to Mr Trump. At a press conference last year, Mr Trump said Mr Pillsbury was “probably the leading authority on China”.
Mr Pillsbury declined to say whether he was asked to raise the issue by the president. The White House did not respond to a request for comment.
Mr Trump has continued to push what most critics say are debunked conspiracy theories about Hunter Biden, in an effort to obtain dirt on the son of Joe Biden, one of the frontrunners for the 2020 Democratic presidential nomination.
The president has faced intense scrutiny about his claims in the two weeks since a CIA whistleblower said Mr Trump had pressured President Volodymyr Zelensky for personal gain, in a move that led White House officials to “lock down” the transcript.
There is no public evidence that Hunter Biden did anything illegal in his business dealings in Ukraine or China. But some critics have said his father should have done more to ensure there was not the perception of a conflict of interest when he was vice-president.
Writing in the Washington Post, Joe Biden rejected any claim of wrongdoing, saying Mr Trump was “pushing flat-out lies, debunked conspiracy theories and smears against me and my family, no doubt hoping to undermine my candidacy for the presidency”.
Asked to provide details about the information he got received from his Chinese contacts, Mr Pillsbury would only say that it related to a $1.5bn payment from the Bank of China. That figure matches the amount that Mr Trump last week claimed Hunter Biden received from China — a statement that has not been backed up with any evidence.
Follow Demetri Sevastopulo on Twitter: @dimi