Hours after US President-elect Donald Trump confirmed that he will appoint his son-in-law Jared Kushner as senior advisor to the president, the Democrats on Tuesday expressed their concern over the incoming White House appointment.

 Leaders on the House Judiciary Committee wrote a letter calling on the Department of Justice and Office of Government Ethics to look into anti-nepotism laws that might limit what Kushner can and cannot do. 

Kushner is married to Trump's older daughter Ivanka Trump and was expected not to take a salary for the post (as communicated by Trump in an official statement), New York Times reported.

The Democrats also asked for a further review of Kushner's potential financial conflicts of interest.

In the letter addressed to the outgoing US Attorney General Loretta E. Lynch, they also asserted that having information, knowledge or influence over the White House's policies might benefit his business holdings .

"For example, it has been reported that he will meet with Speaker of the House Paul Ryan this (Tuesday) evening to discuss tax policy," the letter read.

The Democrats said that this "raises the appearance that he may be using his public office for private gain - namely adopting tax changes which will benefit Kushner and his family".

Earlier Efe news reported that Trump released a statement on Monday that said Kushner would be an "invaluable member of my team as I set and execute an ambitious agenda".

According to his statement, Kushner would work closely with Chief of Staff Reince Priebus and White House chief strategist Stephen Bannon, forming a trio.

Trump also said that this trio would be an effective leadership team. 

It also emphasised the role Kushner had played in the election campaign that culminated in Trump's November 8 win. 

Kushner, an Orthodox Jewish real estate businessman, would have to divest himself from his business activities to take on the government post.

Kushner, who would turn 36 on Tuesday, is the CEO of a company focusing on New York and New Jersey real estate investments and since 2007 he has closed deals worth some $13 billion, according to data from the firm.