Donald Trump’s “demeaning fake orgasm” was “the straw that broke the camel’s back” and made Lisa Page determined to speak out, the former FBI lawyer has said, breaking her silence in a wide-ranging interview with the Daily Beast.

Page told the Beast: “It had been so hard not to defend myself, to let people who hate me control the narrative. I decided to take my power back.”

Page left the FBI in May 2018 amid controversy, driven by Trump, over her role in the Russia investigation and an extra-marital relationship she had with bureau agent Peter Strzok, who went on to work for special counsel Robert Mueller. Strzok was fired in August 2018.

At a rally in Minnesota in October, Trump read from messages between Page and Strzok, from August 2016, three months before the election.

Apparently pretending to have an orgasm, the president said: “I love you, Peter! I love you too Lisa! Lisa, I love you. Lisa, Lisa, Oh God, I love you, Lisa.

“And if [Hillary Clinton] doesn’t win, Lisa, we’ve got an insurance policy, Lisa! We’ll get that son of a bitch out.”

The messages between Strzok and Page were made public during Mueller’s Russia investigation.

In one famous exchange, Page asked: “[Trump’s] not ever going to become president, right? Right?!”

Strzok replied: “No. No he’s not. We’ll stop it.”

The pro-Trump right immediately seized on the messages as evidence of supposed “deep state” bias against the president.

But while the deep state conspiracy theory holds that a permanent government of bureaucrats and intelligence operatives exists to thwart Trump, one of its first proponents, former White House strategist Steve Bannon, has said on record it is “for nut cases”.

Lisa Page is expected to be exonerated of acting unprofessionally or with bias against Trump. Photograph: AP

Being the subject of sustained presidential invective, Page said, was “almost impossible to describe. It’s like being punched in the gut. My heart drops to my stomach when I realise he has tweeted about me again. The president of the United States is calling me names to the entire world. He’s demeaning me and my career. It’s sickening.”

Page, now in private practice, said she “wouldn’t even call [her experience] [post-traumatic stress disorder] because it’s not over. It’s ongoing. It’s not a historical event that is being relived. It just keeps happening”.

Referring to a tweet sent by Trump four days before the interview, she said: “When Roger Stone got convicted, he asked: why isn’t Page in jail too? Not to mention, you know, his truly reprehensible, degrading stunt at his rally, in which he used my name to simulate an orgasm.

“And I don’t ever know when the president’s going to attack next. And when it happens, it can still sort of upend my day. You don’t really get used to it.”

Like most of Washington – and the president – Page is now awaiting the publication on 9 December of a report by the justice department inspector general into Trump’s claim that the FBI spied on his 2016 campaign. Page is expected to be exonerated of acting unprofessionally or with bias against Trump.

Of the political views she exchanged with Strzok, she told the Beast “having an opinion and sharing that opinion publicly or privately with another person is squarely within the permissible bounds” of regulations covering political activity by federal employees.

The Department of Justice was roundly criticised for releasing Page and Strzok’s messages to the press.

Page said it was “very painful to see to places like the FBI and the Department of Justice that represent so much of what is excellent about this country, not fulfilling the critical obligation that they have to speak truth to power”.

She added: “It’s crushing to see the noble justice department, my justice department, the place I grew up in, feel like it’s abandoned its principles of truth and independence.”