US intelligence officials are reported to have warned members of Congress last week that Russia was trying to interfere in the 2020 election campaign in favour of Donald Trump, in a briefing that led to the abrupt removal of the acting director of national intelligence.

When Trump heard about the briefing, he railed at the acting DNI, Joseph Maguire, in the Oval Office, over what the president saw as disloyalty, the Washington Post reported. Until then, Maguire had been a leading candidate to become permanent DNI and is understood to have told colleagues he expected to stay on in the position.

But in the wake of the briefing and Oval Office confrontation, Trump announced the appointment of a hardline loyalist, the US ambassador to Germany, Richard Grenell, in an acting capacity, which does not require Senate confirmation.

According to the New York Times, the briefing last Thursday to the House intelligence committee was delivered by an aide to Maguire, Shelby Pierson, described as having “a reputation for delivering intelligence in somewhat blunt terms”.

The Washington Post reported that Trump had been under the false impression that the briefing had been provided exclusively to the House intelligence committee chair, Adam Schiff, who had acted as chief prosecutor in the president’s impeachment trial. Trump is said to have become convinced that the briefing would be used against him in the election.

Unlike Maguire, a retired vice-admiral who ran the National Counterterrorism Center, Grenell has no intelligence experience (he was a spokesman for the US mission at the UN before being named ambassador) and is an outspoken partisan, particularly on social media.

“So the Grenell appointment is exactly what it looks like – a bid to politicize intelligence and hide information from Congress in an election year where Russia is again helping Trump,” said Matthew Miller, a former justice department spokesman, in a tweet.

According to the New York Times account, last week’s briefing was contentious, with Trump’s allies on the intelligence committee challenging the conclusions, arguing that the administration had been tough on Russia.

As Grenell was confirmed in his ambassadorial job, the president has the authority to install him as acting DNI under the Federal Vacancies Reform Act, but under the same act, he can only serve until 11 March, unless the president formally nominates a candidate for the permanent position. If a nomination is being reviewed by the Senate, the acting director could stay in the post for a few more months during the confirmation process.

Grenell said on Twitter that “the president will announce the nominee (not me) sometime soon”.