And so trouble piles up for Donald Trump in the wake of his Wednesday charge, seemingly unfounded, that the agencies were responsible for leaking a damaging – and unverified – intelligence dossier which claims that he frolicked with prostitutes in Moscow in 2013; and that his campaign might have been a party to Russian efforts last year to derail Hillary Clinton's presidential campaign.

A point of acute anxiety for Trump is that any suggestion, unfounded or not, that he had a leg-up in winning the election risks diminishing what he likes to bill as one of the most remarkable election wins ever – never mind that Clinton won almost three million more votes than Trump in the national popular vote.

But news on Thursday that Department of Justice inspector general Michael Horowitz has launched a review of the FBI's handling of its investigation of Clinton's controversial private email server risks further tarnishing Trump's "greatest" victory – because if the FBI's conduct is faulted in any way, it could lend credence to Democrat claims that Clinton was robbed of victory by the bizarre pre-election behaviour of FBI director James Comey.

Recall that in July, Comey went against Department of Justice protocols by holding a sensational press conference at which, on the one hand, he handed defensive ammunition to Clinton, by clearing her of criminal wrongdoing; but on the other, he provided attack ammunition to Trump, by savaging Clinton for her "extremely careless" handling of her email.

And that in the days before the November 8 election, front-runner Clinton's polling took a dive when Comey strode back into the public spotlight, releasing a letter he wrote to congressional leaders effectively saying, "can you believe it – we're re-opening the Clinton inquiry because we've found another laptop with hundreds of thousands more emails that could be relevant to the earlier investigation ".

And then three days before the vote, another letter – and this time Comey was saying, "ah shucks, you're not going to believe it, none of the new emails are relevant".

It's not clear what Comey had for lunch on Thursday. But given reports that colleagues had warned him not to release the election-eve letters; and given informed speculation, by the likes of The Washington Post's Chris Cillizza, that "it's virtually impossible to defend his decision to make such a show of a discovery that, ultimately, amounted to nothing," a statement released by Comey read as if it had been written after a fun lunch.

"I'm grateful to the Department of Justice's IG for taking on this review. He is professional and independent and the FBI will co-operate fully with him and his office," the statement reads.

"I hope very much he's able to share his conclusions and observations with the public because everyone will benefit from thoughtful evaluation and transparency regarding this matter."

But the weird selectivity in Comey's thinking was on display again this week. With so much swirling about Trump and his campaign, it was perfectly logical for members of congress to ask if the FBI was investigating any of it.

"I don't, especially in a public forum…we never confirm or deny a pending investigation," he said. And he might as well have added: "Unless the suspect's name begins with the letter C."

Horowitz said he would not be attempting to second-guess the decision not to charge Clinton. Instead, according to various reports, he will examine Comey's press conference and letters to congress; leaks from the FBI, possibly including Trump surrogate Rudi Giuliani's access to inside information; an internal FBI conflict over management's rejection of a push by field agents to investigate the Clinton family foundation; and the propriety of the FBI's congressional liaison officer passing information to the Clinton campaign.

Intelligence officials have explained that the nature of the content of the 35-page dossier on alleged Russian efforts to compromise Trump meant they were duty-bound to attach a two-page summary of its contents to last week's intelligence briefing to Trump…and outgoing president Barack Obama [who must have had a great laugh] and eight Congressional leaders. At the same time, there'll also be suspicion that the attachment was payback for Trump's juvenile mocking of the services on which, ordinarily, he would rely for intelligence as president.

For now, it's unclear how the various agencies will proceed in investigating the contents of the Russia dossier – according to the BBC, an interagency task force was established last year because of it's overlapping domestic and foreign aspects.

And though many US reporters have possessed copies of the dossier since last year, it had stayed out of the news for want of verification. However, some editors can be relied on to resume seeking to verify elements of the dossier, in the belief that this week's sensational publicity about its existence might loosen lips that previously had been shut tight.

With just a week to Trump's inauguration, Vicki Divoll, formerly an attorney for both the CIA and the Senate intelligence panel, didn't see how Trump and the agencies could bury the hatchet.

"After disparaging and demeaning the hardworking officers of the intelligence community, then grudgingly accepting their conclusions about Russian election hacking, Mr Trump is now hurling the worst epithet out there – comparisons to Nazi Germany – against them, without basis and on the eve of taking office," Divoll told The Guardian.

"We are at our peril to be entering an era in which there is such open, irrational and hysterical hostility by a president against a community of 17 agencies whose mandate is to keep us safe."