Mr Bannon and three others defrauded hundreds of thousands of donors in connection with the "We Build the Wall" campaign, which raised $25m (£19m), the US Department of Justice (DoJ) said.

Mr Bannon received more than $1m, at least some of which he used to cover personal expenses, the DoJ said.

He is due to appear in court later.

Steve Bannon, Brian Kolfage, Andrew Badolato and Timothy Shea are charged with one count of conspiracy to commit wire fraud and one count of conspiracy to commit money laundering, each of which carries a maximum penalty of 20 years in prison.

Mr Kolfage - founder of "We Build the Wall" - allegedly took $350,000 for his personal use.

The "We build the wall" campaign pledged to use donations to build segments of the border barrier - whose construction was a key Trump promise during the 2016 election - on private land.

In all, 14 Trump aides, donors and advisers have been indicted or imprisoned since the days when the first-time candidate promised that he would only hire "the best people."

The We Build the Wall campaign started in 2018 as a GoFundMe by Kolfage, a military veteran, who has described some people crossing the southern border without documents as terrorists and drug traffickers and accused border wall critics as being cartel collaborators. The campaign created a video posted on YouTube of construction of metal barricades to attract anti-immigrant donors to the campaign.

After Kolfage brought Bannon and Badolato into the fundraising campaign, “within days”, the pair gained “significant control” of this fundraiser, such as its messaging, donor outreach and finances, according to the indictment.

By spring 2019, the group had raised $22m out of its $1bn goal.

In a secret deal with the others, Kolfage, it was alleged, “covertly took for his personal use more than $350,000 in funds that donors had given to We Build the Wall”. To hide this, the men “devised a scheme” to direct money siphoned from We Build the Wall to Kolfage through a non-profit and a shell company that Shea controlled, using bogus invoices and “sham” vendor agreements.

Kolfage used the money for expenses, such as “home renovations, payments toward a boat, a luxury SUV, a golf cart, jewelry, cosmetic surgery, personal tax payments and credit card debt”. The other men each siphoned “hundreds of thousands” in donations, it was said, which they used on personal expenses such as “travel, hotels, consumer goods and personal credit card debts”.

When the men realized that they might be under federal investigation in October 2019, they tried hiding their scheme, using encrypted messaging apps.

The White House press secretary, Kayleigh McEnany, distanced the president from the scheme, saying he had “not been involved” with Bannon since the campaign and the early part of the administration, and he did not know the other people.

She said: “As everyone knows, President Trump has no involvement in this project and felt it was only being done in order to showboat, and perhaps raise funds. President Trump has previously and publicly stated the following: ‘I disagreed with doing this very small (tiny) section of wall, in a tricky area, by a private group which raised money by ads. It was only done to make me look bad, and perhaps it now doesn’t even work.’”

Mr. Kobach, a hard-line ally of President Trump known for his strident stand on immigration, has long advocated a tough border policy.

He is currently an advisory board member of “We Build the Wall Inc.” a nonprofit group that has collected more than $12 million toward the effort. Mr. Kobach says the group has obtained the presidential seal of approval for the private initiative.

President Trump gave the undertaking his “blessing” in a telephone conversation Wednesday night, according to Mr. Kobach.

Steve Bannon’s arrest on charges that he defrauded donors to a right-wing immigration group for $1 million marks the end of a political era—the era when a Trumpian admixture of economic populism and nativist immigration policy looked as if it could, as Bannon once put it to me, deliver the Republican Party “a hammerlock on the Electoral College.”

At the time he made this assessment, in the days after Trump’s 2016 victory, it seemed entirely plausible that Bannon, Donald Trump’s campaign chairman and future chief strategist, was right. Before Trump, the GOP had imagined its future lay in purging its racist fringe and soft-pedaling its brand of laissez-faire economics to a diversifying nation that had spurned the 2012 Republican ticket of Mitt Romney and Paul Ryan. The Republican Party “autopsy” conducted in 2013 after their loss warned that the GOP risked falling into oblivion if it didn’t present a more welcoming face to immigrants, minorities, and young people.

Trump, of course, egged on by Bannon, instead offered a turbocharged anti-immigrant nationalism that promised to revive working-class fortunes, a message that resonated particularly among Rust Belt voters who’d previously voted Democratic.

Had Trump delivered on his promise and instituted the kind of working-class populism Bannon was espousing in 2016, he’d likely be in a better position than he is today. Certainly, Bannon would be. But that never happened. “There was only a plan to get elected,” says Sam Nunberg, a former Trump staffer. “There was never a plan to govern.”

Instead, the Trump administration proved chaotic from the outset and the Trump-Bannon marriage quickly blew apart. Once in office, Trump lost any interest he’d had in economic populism and signed a tax cut that favored the rich, while Bannon, who clashed with colleagues and members of Trump’s family and had no experience in or talent for policymaking, was quickly forced out of his chief strategist job.

The symbolism of Bannon’s grand political project ending in his indictment and arrest is timely, if nothing else. Precisely four years ago, he’d just taken command of Trump’s sputtering, left-for-dead presidential campaign and was about to steer it to the greatest upset in U.S. political history.

But the political realignment Bannon thought was happening four years ago always depended on Trump delivering what he’d campaigned on. The details of Bannon’s indictment lay bare the path he’s traveled since the days not so long ago when he was regarded in some circles as “the second most powerful man in the world.”