Elon Musk is not an official employee of the Department of Government Efficiency (Doge) and has "no formal authority to make government decisions," according to a White House court filing.

The world's richest man is widely seen as the de-facto head of Doge, created by President Donald Trump, which has sought to drastically reduce US government spending including with thousands of job cuts.

Trump had announced in November that "the Great Elon Musk... will lead the Department of Government Efficiency ('DOGE')."

According to the filing on Monday by Joshua Fisher, director of the Office of Administration, Musk "is an employee of the White House... as a non-career Special Government Employee" and a "Senior Advisor to the President."

"Like other senior White House advisors, Mr Musk has no actual or formal authority to make government decisions himself. Mr Musk can only advise the President and communicate the President's directives," Fisher said.

"The US Doge Service is a component of the Executive Office of the President. The US Doge Service Temporary Organisation is within the US Doge Service. Both are separate from the White House Office," he said in the filing.

"Mr Musk is an employee of the White House Office. He is not an employee of the US Doge Service or US Doge Service Temporary Organisation. Mr Musk is not the Temporary Administrator," he added.

Fisher's filing was made in a case brought against Musk by 14 US states, including New Mexico.

In a joint interview with Musk due to be broadcast on Fox News later on Tuesday, Trump took aim at critics saying that the Tesla founder was the one running the White House.

"I think nobody in history has ever gotten more bad publicity than me... But you know what I have learned Elon? That people are smart, they get it," Trump said in an excerpt of the interview.

Musk added: "Yeah they do actually." (AFP)