Donald Trump was unaware his former national security adviser, General Michael Flynn, who resigned last month, was acting as a “foreign agent” for another foreign country, the US President's spokesman has said.

Mr Flynn, a retired army general, told the US Justice Department’s Foreign Agent Registration Unit he received $530,000 to lobby on behalf of a Turkish company – just weeks before he was appointed as Mr Trump’s most senior national security aide.

The US President’s spokesman insisted the Mr Trump was unaware that his close adviser was a “foreign agent”.

The paperwork, filed voluntarily by Mr Flynn’s lawyer, said the retired general had carried out work between August and November 2016 that “could be construed to have principally benefited the Republic of Turkey”.

US law states any citizen working on behalf of a foreign government or political entity must register with the Justice Department, and failure to do so is a criminal offence.

Mr Flynn worked on behalf of a Turkish company rather than the government, but the nature of the work was deemed to be potentially beneficial to the state.

Ekim Alptekin, the businessman who employed Flynn Intel Group Ltd., told the Associated Press the documents were a response to "political pressure" and he did not agree with Mr Flynn's decision to register with the Justice Department.

"I disagree with the filing," he said. "It would be different if I was working for the government, but I am not taking directions from anyone in the government."

In pictures: Protests, pomp and Donald Trump Show all 30 1 /30 In pictures: Protests, pomp and Donald Trump In pictures: Protests, pomp and Donald Trump President-elect Donald Trump acknowledges guests as he arrives on the platform at the US Capitol in Washington DC Getty Images In pictures: Protests, pomp and Donald Trump Donald Trump is sworn in as the 45th president of the United States by Chief Justice John Roberts as Melania Trump looks on during the 58th Presidential Inauguration at the U.S. Capitol in Washington AP In pictures: Protests, pomp and Donald Trump President Donald Trump shakes hands with Justice John Roberts after taking the oath at inauguration ceremonies swearing in Trump as the 45th president of the United States Reuters In pictures: Protests, pomp and Donald Trump President Donald Trump raises his fists after his inauguration on the West Front of the U.S. Capitol Getty In pictures: Protests, pomp and Donald Trump U.S. President-elect Donald Trump greets outgoing President Barack Obama before Trump is inaugurated during ceremonies on the Capitol in Washington Reuters In pictures: Protests, pomp and Donald Trump resident-elect Donald Trump arrives on the platform of the US Capitol in Washington DC Getty Images In pictures: Protests, pomp and Donald Trump Attendees partake in the inauguration ceremonies to swear in Donald Trump as the 45th president of the United States at the U.S. Capitol in Washington DC Reuters In pictures: Protests, pomp and Donald Trump US President Donald Trump delivers his inaugural address during ceremonies at the US Capitol in Washington DC Getty In pictures: Protests, pomp and Donald Trump U.S. President Donald Trump waves with wife Melania during the Inaugural Parade in Washington DC Reuters In pictures: Protests, pomp and Donald Trump Protesters registered their rage against the new president Friday in a chaotic confrontation with police who used pepper spray and stun grenades in a melee just blocks from Donald Trump's inaugural parade route. Scores were arrested for trashing property and attacking officers AP In pictures: Protests, pomp and Donald Trump Demonstrators protest against US President Donald Trump in Washington DC Getty Images In pictures: Protests, pomp and Donald Trump A woman holds a sign before the start of the Presidential Inauguration of Donald Trump at Freedom Plaza in Washington DC Getty Images In pictures: Protests, pomp and Donald Trump Anti-Trump protesters prepare banners for a protest against the inauguration of US President-elect Donald Trump, in Berlin REUTERS In pictures: Protests, pomp and Donald Trump Demonstrators shout slogans against US President-elect Donald Trump in Washington DC Getty Images In pictures: Protests, pomp and Donald Trump Demonstrators march, block foot traffic and clash with U.S. Capitol Police at the entry checkpoints for the Inauguration of Donald Trump Alamy Live News In pictures: Protests, pomp and Donald Trump Demonstrators display a banner as people arrive for US President-elect Donald Trump's inauguration in Washington DC Getty Images In pictures: Protests, pomp and Donald Trump A man displays a placard as people lineup to get into the National Mall for the inauguration of US President-elect Donald Trump in Washington DC Getty Images In pictures: Protests, pomp and Donald Trump Protesters demonstrating against U.S. President Donald Trump raise their hands as they are surrounded by police on the sidelines of the inauguration in Washington DC Reuters In pictures: Protests, pomp and Donald Trump A demonstrator wearing a mask depicting Donald Trump protests outside the US Embassy in London Getty Images In pictures: Protests, pomp and Donald Trump Demonstrators hold placards as they protest outside the US Embassy in London Getty Images In pictures: Protests, pomp and Donald Trump Former US President George W. Bush and First Lady Laura Bush arrive for the Presidential Inauguration at the US Capitol Rex In pictures: Protests, pomp and Donald Trump Michelle Obama and Dr. Jill Biden share an umbrella as President Donald Trump delivers his inaugural address at the inauguration in Washington DC Rex In pictures: Protests, pomp and Donald Trump Former Democratic presidential nominee Hillary Clinton and former President Bill Clinton arrive on the West Front of the U.S. Capitol in Washington Reuters In pictures: Protests, pomp and Donald Trump U.S. Vice President Mike Pence takes the oath of office on the West Front of the U.S. Capitol in Washington, DC Getty Images In pictures: Protests, pomp and Donald Trump Advisors to President-elect Donald Trump, Kellyanne Conway and Steve Bannon depart from services at St. John's Church during the Presidential Inauguration in Washington Reuters In pictures: Protests, pomp and Donald Trump Protesters demonstrating against U.S. President Donald Trump take cover as they are hit by pepper spray by police on the sidelines of the inauguration in Washington DC Reuters In pictures: Protests, pomp and Donald Trump An activist demonstrating against U.S. President Donald Trump is helped after being hit by pepper spray on the sidelines of the inauguration in Washington DC Reuters In pictures: Protests, pomp and Donald Trump A police officer tries to tackle a protester demonstrating against U.S. President Donald Trump Reuters/Adrees Latif In pictures: Protests, pomp and Donald Trump Police arrest and detain a protester in the street in Washington DC Rex In pictures: Protests, pomp and Donald Trump A police officer falls to the ground as another shoots pepper spray at protesters demonstrating against U.S. President Donald Trump on the sidelines of the inauguration in Washington DC Reuters

Mr Alptekin added that he had asked for some of the $530,000 in payments to the Flynn Intel Group to be returned to him because he was unhappy with the company's performance.

Asked at the White House daily briefing on Thursday whether Mr Trump had known about his adviser’s other role, the President’s press secretary, Sean Spicer, said: “I don’t believe that was known.”

Mr Flynn was forced to resign last month after it was revealed he had lied about the nature of his contacts with Russian officials. The former general had insisted he had not discussed the issue of US sanctions against Russia with Sergey Kislyak, Moscow’s ambassador to the US, in the weeks before formally taking office. However, leaked intelligence intercepts showed this was untrue.

The newly-filed documents show Mr Flynn met with at least two Turkish government ministers in September, at a time when he was also working as an adviser to Mr Trump.

Donald Trump is questioned over whether he ordered General Flynn to discuss sanctions with Russia

The work he carried out involved collecting information on Fethullah Gulen, a Muslim cleric who Turkey accuses of being behind a failed coup in July 2016, and lobbying American officials to take action against him.

At the time he was being paid by Mr Alptekin, Mr Flynn also wrote an opinion article for The Hill, the US online political newspaper, praising Turkey and urging closer co-operation with the country.

“We need to adjust our foreign policy to recognise Turkey as a priority, he wrote. “We need to see the world from Turkey’s perspective.