Democrats have called for US President-elect Donald Trump's naming of his son-in-law as a top adviser to be reviewed over concerns of nepotism and conflict of interest.
A group of lawmakers wants the Justice Department and Office of Government Ethics to scrutinise "legal issues" related to the appointment of Jared Kushner, 36.
His lawyer says the post does not breach anti-nepotism laws.
Mr Kushner is married to Mr Trump's daughter Ivanka.
The millionaire would step down as boss of his family's real estate business and publisher of the New York Observer in order to comply with ethics laws, his lawyer Jamie Gorelick said.
He would also divest "substantial assets", she said.
In his new role, he would initially focus on trade policy and the Middle East, according to officials from the transition team.
Mr Trump will be inaugurated as the 45th president on 20 January.
Several of his Cabinet picks have business interests that will be scrutinised at confirmation hearings taking place this week.
Mr Trump's pick for attorney general, Alabama Senator Jeff Sessions, is first to face Senate confirmation hearings on Tuesday. He was turned down for a federal judgeship in 1986 because of alleged racist remarks.
Unlike Cabinet positions, advisers are considered part of White House staff and do not require approval from Congress.
Softly-spoken and usually camera-shy, Mr Kushner is a vastly wealthy property developer and publisher who played an influential role in Mr Trump's presidential campaign and has been included in key meetings with foreign leaders during the transition period.
An Orthodox Jew whose grandparents were Holocaust survivors, he was raised in Livingston, New Jersey, and went on to study sociology at Harvard.
His father, also a property mogul, was jailed for tax evasion, illegal campaign contributions and witness tampering in 2005 by Chris Christie - then the US attorney for New Jersey.
Jared Kushner is said to have played a key role in the ousting of Mr Christie, by then New Jersey governor, from Mr Trump's presidential campaign team last year.
On Sunday, Mr Kushner and Mr Trump's chief strategist Steve Bannon met UK Foreign Secretary Boris Johnson.
Democrats in the US Congress have called for the Justice Department to consider whether Mr Kushner's appointment violates nepotism laws.
In their letter, the Democratic lawmakers, all members of the House Judiciary Committee, argue that a "strong case" can be made that a 1967 federal anti-nepotism statute applies to staff working in the White House, a position rejected by Mr Trump's team.
They also raise questions about how, even with significant divestment, he could completely avoid conflicts of interest in his White House role.
Ms Gorelick said Mr Kushner was committed to complying with federal ethics laws and had consulted with the Office of Government Ethics about what steps to take.
She added he would not be paid for the advisory role.
No post for Ivanka
Ivanka Trump will step down from executive roles at the Trump Organization as well as her own fashion brands.
But she will not be taking an official role in her father's government and instead will focus on raising her children.
Reports said last week that Ivanka and Jared and their children would be moving into a $US5.5 million ($NZ7.8m) home in Washington DC's wealthy Kalorama neighbourhood - at least for some time. The Obama family are due to be moving to the same area after leaving the White House.
Meanwhile, Mr Trump announced in November that his wife, Melania, would be staying in New York - at least initially - after his inauguration to allow their youngest son, Barron, to finish the school year.
What is the nepotism law?