The White House has struck back against congressional Republicans for considering an impeachment of President Joe Biden, urging the media to scrutinise an "inquiry based on lies".

"It is the responsibility of the independent press to treat their claims with appropriate scrutiny," top aide Ian Sams wrote.

House of Representatives Speaker Kevin McCarthy announced the investigation into Mr Biden, a Democrat, on Tuesday.

But there is dissent among Republicans.

Some rank-and-file lawmakers question whether they have sufficient evidence to impeach the president.

It is not uncommon for White House press officials to outline their case to journalists, but the 16-page document shows how seriously they are taking the impeachment threat.

Mr Sams, a special assistant to the president, addressed the memo to "editorial leaders at US news media organisations".

"After nearly nine months of investigating, House Republicans haven't been able to turn up any evidence of the President doing anything wrong," Mr Sams wrote.

"For years, Republicans in Congress have tried to muddy the waters by attracting media coverage of their allegations, and as they choose to move forward with impeachment, it is the responsibility of the independent press to treat their claims with the appropriate scrutiny," he wrote.

Mr Sams included multiple pages of rebuttals to Republicans' claims.

At a campaign event on Wednesday, Mr Biden told journalists that Republicans have long hoped to impeach him.

"First they just wanted to impeach me," he said.

"Now best as I can tell, they want to impeach me because they want to shut down the government."

Republicans have long scrutinised President Biden's son, Hunter Biden, for his business dealings abroad.

They argue he improperly used his father's influence to secure deals and enrich himself, and have spent the past nine months holding hearings and investigations through the House oversight committee.

Hunter Biden is expected to soon face federal gun charges after a plea deal for a firearms-related crime and separate tax violations recently fell apart in court.

Conservatives in Congress have spent several months attempting to link Hunter Biden's actions to his father, but have so far not revealed any concrete evidence that implicates the president in any wrongdoing.

Still, right-wing Republicans in Congress have increasingly agitated for impeaching Mr Biden, and Mr McCarthy has now supported that effort.

They have unveiled their primary allegations against Mr Biden, but have not yet moved forward with voting on articles of impeachment.

Republicans who support impeachment accuse the Biden family of "influence peddling" abroad and enriching themselves from foreign sources.

They also allege that Joe Biden participated in phone calls with Hunter Biden's business associates to benefit his son, stymied the investigation into his son's taxes and took part in an alleged - but unsubstantiated - bribery scheme.

US outlet Axios reported Wednesday that two claims previously made by Joe Biden - that he had not met any of his son's Ukrainian business associates while vice-president, except maybe for a brief hello, and that his son had not made any money from China - were false, according to testimony from Hunter Biden and his business partner Devon Archer.

But Mr Archer, who was convicted on federal tax crimes, also told a closed-door congressional hearing in July he was not aware of any wrongdoing by Joe Biden.

He made the remarks during a closed-door congressional hearing in July, the New York Times reported.

The White House pushed back against these allegations, outlining their rebuttals in Wednesday's memo.

"It's clear that this 'investigation' is all politics and no evidence," Mr Sams wrote.

Several Republicans have voiced scepticism that their colleagues have gathered enough evidence to impeach the president - one was quoted in the White House memo.

It highlighted remarks by Colorado lawmaker Ken Buck, who told MSNBC: "The time for impeachment is the time when there's evidence linking President Biden - if there's evidence linking President Biden - to a high crime or misdemeanour.

"That doesn't exist right now."

While Senate Republicans have not unanimously gotten behind an impeachment effort, they appear receptive to learning more as the inquiry proceeds.

Two-thirds of the US Senate must vote to convict on articles of impeachment, and as it stands, Republicans are in the minority in the chamber.

Rep James Comer, the Republican leading the House efforts, briefed their Senate counterparts on the investigation on Wednesday.

Some lawmakers appeared open to their efforts.

Senator Lindsey Graham, a South Carolina Republican, told the AP that he believed House Republicans were "better off having a vote. It does give it more legitimacy".