The White House has defended its role in helping to broker a deal that will shroud art deals by President Joe Biden's son in secrecy.
Paintings by Hunter Biden are expected to fetch up to $500,000 (£360,000) apiece at auction this autumn.
The president's spokeswoman said "reasonable safeguards" had been applied to the upcoming sale.
But a former White House ethics chief said the arrangement was "very disappointing".
The younger Biden's business dealings in Ukraine, China and elsewhere have often been held up by Republican critics as a conflict of interest for his father, which both Bidens deny.
Hunter is currently facing a federal tax investigation, though he has said he is "100% certain" he will be cleared.
When asked on Friday about the White House's reported role in the art sale, press secretary Jen Psaki said: "After careful consideration, a system has been established that allows for Hunter Biden to work in his profession within reasonable safeguards.
"Of course, he has the right to pursue an artistic career just like any child of a president has the right to pursue a career."
As part of the arrangement, the buyers are supposed to remain anonymous to Hunter Biden – who is a self-taught artist – in order to prevent influence-peddlers seeking to curry favour with the US president.
"I think it would be challenging for an anonymous person who we don't know and Hunter Biden doesn't know to have influence," Ms Psaki said.
But Walter Shaub, who served as ethics chief under President Barack Obama, rejected the White House's claim that the arrangement would ensure transparency.
Mr Shaub, who was an outspoken critic of former President Donald Trump, wrote on Twitter: "So instead of disclosing who is paying outrageous sums for Hunter Biden's artwork so that we could monitor whether the purchasers are gaining access to government, the [White House] tried to make sure we will never know who they are.
"That's very disappointing."
Hunter's first solo exhibition and auction is set for October at the George Bergès Gallery in New York.
The gallery describes the oil, acrylic and ink paintings as "a distinctively unique experience that have become signature Biden".
According to the dealer, smaller pieces are set to sell for $75,000, with the larger ones expected to reach half a million dollars.
The younger Biden, 51, published a memoir in April detailing his struggles as a crack cocaine addict.