Donald Trump continued to attack the former CIA director John Brennan on Monday, seemingly in response to the release of a remarkable open letter criticizing the president’s decision last week to revoke Brennan’s security clearance.

The letter, signed by 177 former national security officials appointed by both Republicans and Democrats, accused Trump of acting against Brennan because Brennan had criticized him. The signatories stated “our firm belief that the country will be weakened if there is a political litmus test applied before seasoned experts are allowed to share their views”.

In the US intelligence community, revolt against the president is brewing. Monday’s letter followed a similar missive that was released last week by senior figures including six former directors and five former deputy directors of central intelligence and a former director of national intelligence. Trump’s move against Brennan also provoked a stinging Washington Post column by Adm William H McRaven, the leader of the operation to kill Osama Bin Laden.

On Sunday, Brennan threatened to challenge the revocation of his security clearance in court, charging Trump with wielding his power in an attempt to chill free speech.

In a Twitter rant following others about special counsel Robert Mueller and the New York Times, Trump called Brennan – previously a CIA station chief in Riyadh, Saudi Arabia; acting director of the National Counterterrorism Center under George W Bush; and homeland security adviser to Barack Obama – a “political ‘hack’”.

“I hope John Brennan, the worst CIA Director in our country’s history, brings a lawsuit,” the president tweeted. “It will then be very easy to get all of his records, texts, emails and documents to show not only the poor job he did, but how he was involved with the Mueller Rigged Witch Hunt. He won’t sue!”

Trump’s tweet seemed riddled with misunderstandings and inaccuracies.

Brennan did not threaten to sue Trump personally but to make a case in court that Trump had abused his executive power by revoking his security clearance in response to criticism.

Later on Monday, Trump used Twitter to threaten another former intelligence official, Philip Mudd, with the revocation of his security clearance. Apparently referring to an argument on CNN between the Republican strategist Paris Dennard and Mudd, Trump wrote: “Just watched former Intelligence Official Phillip Mudd become totally unglued and weird while debating wonderful @ PARISDENNARD over Brennan’s Security Clearance. Dennard destroyed him but Mudd is in no mental condition to have such a Clearance. Should be REVOKED?”

Legal analysts warned that Trump’s move could ultimately weaken the presidency by opening the way for an expanded role for the courts in the clearances process.

Brennan did not threaten to sue Trump personally but to make a case in court that Trump had abused his executive power by revoking his security clearance in response to criticism. Photograph: Kevin Lamarque/Reuters

It is not clear how any such legal action would result in the disclosure of Brennan’s “texts, emails and documents” shedding light on his job performance.

With the notion that such material would demonstrate that a CIA director who left office five months before the appointment by Trump’s own justice department of a special counsel would reveal “how [Brennan] was involved with the Mueller Rigged Witch Hunt”, Trump entered the realm of conspiracy mongering.

Trump went on to accuse the 177 former national security officials who signed the open letter of being motivated by the “big dollars” he said their security clearances afforded them.

“Everybody wants to keep their Security Clearance, it’s worth great prestige and big dollars, even board seats, and that is why certain people are coming forward to protect Brennan,” he tweeted. “It certainly isn’t because of the good job he did! He is a political “hack.”

Service in the national security sector is not notorious for being highly remunerative, as Michael Flynn, Trump’s former national security adviser, and many others have demonstrated. Flynn has said he needs help to pay legal fees arising from his guilty plea to lying to the FBI, made as part of a deal with Mueller’s team.

One signatory to the Monday letter, former CIA officer David Priess, responded on Twitter: “Sorry, sir. My post-employment security clearance, when I had it, granted me neither ‘great prestige’ nor ‘big dollars’ nor ‘board seats’. I can’t speak for other signers, but this certain person came forward not for any of that, but to voice concern about an abuse of power.”

Trump also criticized Jeff Sessions, the attorney general he has previously targeted for his decision to recuse himself from the Russia investigation, and Bruce Ohr, a justice department official whose wife once worked for a firm that paid in part for a private investigation of an alleged campaign by Russian intelligence operatives to gain influence over Trump in the years before he entered politics.

That investigation is known as the Steele dossier after Christopher Steele, the former MI6 agent who compiled it. Trump routinely rails against the dossier and believes its existence demonstrates a “deep state” plot to destroy his campaign and presidency.

“Will Bruce Ohr, whose family received big money for helping to create the phony, dirty and discredited Dossier, ever be fired from the Jeff Sessions ‘Justice’ Department?” Trump tweeted. “A total joke!”

As midday neared – and with it a scheduled lunch with his vice-president, Mike Pence – Trump appeared to be watching Fox News. Seemingly undeterred by his wife Melania’s appearance earlier at a summit on the prevention of cyberbullying, he concluded his rant (or marked a pause at least) with an accusation against Ohr that a Republican congressman had just made on the network.

“‘Bruce Ohr is at the center of FALSE ALLEGATIONS which led to a multi-million dollar investigation into what apparently didn’t happen’,” Trump tweeted, concluding: “Darrell Issa, House Oversight. We can take out the word ‘apparently.’ @FoxNews.”

Issa, who is not running for re-election, has not led the House oversight committee for three and a half years.