Kushner Companies, received substantial loans from Citigroup and private equity group Apollo Global Management last year, The New York Times reported.
Apollo's $184m (£133m) loan in November was to help refinance the mortgage on a Chicago skyscraper and Citigroup's $325m (£236m) in the spring of 2017, went towards financing office buildings in New York.
One of the founders of Apollo Global Management, Joshua Harris, made frequent visits to the White House early last year, the newspaper reported.
Sources told The Times that Mr Kushner, whose security clearance was downgraded earlier this week, discussed the possibility of a White House job for the private equity billionaire.
“This is exactly why senior government officials, for as long back as I have any experience, don’t maintain any active outside business interests," Don Fox, former acting director of the Office of Government Ethics under Barack Obama, told the newspaper. "The appearance of conflicts of interest is simply too great.”
But a spokesperson for Mr Kushner's lawyer said he "has taken no part of any business, loans or projects with or for" Kushner Companies since joining the White House.
The real estate developer who is married to Ivanka Trump, resigned as chief executive of Kushner Companies, became a White House adviser last year.
He sold a small portion of his stake in the firm to a trust controlled by his mother, but the 37-year-old maintained the vast majority of his interest in the firm.
An Apollo spokesperson said Mr Harris was not involved in the decision to loan funds to Kushner Companies and the loan “went through the firm’s standard approval process.”
A spokesperson for Citigroup said Kushner Companies had been a client before the election and that the relationship had no connection to Mr. Kushner’s White House role.
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