Donald Trump takes office when there is reported to be a broad investigation into possible collusion between the Kremlin and campaign officials

The new president can stop all executive investigations. Will he halt ones about himself?

President Donald Trump takes office in circumstances unlike any in US history. He assumes executive authority, and his nuclear launch codes are being activated at a time when there is reported to be a broad, multi-agency investigation into possible collusion between the Kremlin and officials on his campaign.

US intelligence agencies have already concluded that Vladimir Putin interfered in the presidential election in Trump’s favour. The night before his inauguration, the New York Times quoted current and former senior US officials as saying that law enforcement and intelligence agencies were examining intercepted communications and financial transactions as part of their inquiries.

Donald Trump inauguration: 'America first and only America first' – president's first speech live Read more

On Wednesday, the McClatchy news agency reported that the FBI and five other agencies had been collaborating for months in an investigation into the extent of Russian attempts to skew the election. The report said that investigators were examining how money may have been transferred by the Kremlin in its covert bid to help Trump win. One possibility was that a system used to pay Russian-American pensioners was used to pay email hackers in the US.

Once Trump takes the reins of power, however, he has the authority to stop all executive branch investigations.

He could replace the FBI director, James Comey, although it is highly unusual for a FBI chief to be fired before the end of his 10-year term. Bill Clinton sacked director William Sessions in 1993, on the basis of an investigation into his conduct carried out under George HW Bush into alleged abuse of office. However, barring evidence of blatant wrongdoing by Comey, any move by Trump to dismiss him while the president’s associates were under investigation would be highly controversial, akin to Richard Nixon’s dismissal of special prosecutor Archibald Cox in 1973.

Congress has also launched its own investigations. The Senate intelligence committee announced last week that it planned to interview senior figures in the incoming administration as part of its inquiry into Russian hacking of the election, and a subcommittee of the armed services committee, run by Trump’s Republican nemesis, Senator John McCain, is pursuing a parallel enquiry.

On 9 December, McCain personally handed Comey a set of reports alleging the Trump campaign’s collusion with Moscow, compiled by former MI6 officer Christopher Steele, as part of opposition research conducted by the campaign, although the FBI had first received the reports months earlier.

DeploraBall: Trump lovers and haters clash at Washington DC event Read more

However, according to press reports, the joint investigation was launched before the Steele reports were written, and based on intelligence collected independently by US and allied agencies.

The BBC has reported that the justice department was granted a warrant by the Foreign Intelligence Surveillance Act (Fisa) court, in October to monitor two Russian banks suspected of being involved in Moscow’s intervention. The issue of the Fisa warrant was first reported on the eve of the election by former British MP, Louise Mensch, on the Heatstreet news website.

The Guardian’s own sources have confirmed the first application for a warrant over the summer, but not the granting of a warrant in October.

According to the New York Times, the joint investigation into links with Moscow includes the former Trump campaign manager, Paul Manafort, who had a long history of working for pro-Russian public figures in Ukraine.

Manafort did not reply to a Guardian request for comment, but told the New York Times in an email that the allegations of collusion with Moscow were a “Democrat Party dirty trick and completely false.”

“I have never had any relationship with the Russian government or any Russian officials. I was never in contact with anyone, or directed anyone to be in contact with anyone,” he said.

Manafort stood down from his campaign post in August, but one of his close friends has confirmed to the Guardian that he continues to provide advice to Trump informally.