The former national security adviser John Bolton acknowledged intense speculation “about what I plan to do next” in a tweet on Saturday morning, but to the disappointment of many did not follow up by saying he would testify in the impeachment inquiry against Donald Trump.

Instead, the moustachioed Bush veteran and foreign policy hawk linked to his own political action committee, John Bolton Pac, which seeks “to identify and support Senate and House candidates committed to policies promoting a strong America”.

Reaction was predictably downbeat, the writer Molly Jong Fast responding: “Testify, testify, testify.”

The former ambassador to the UN and Fox News contributor became the president’s third national security adviser in April 2018. He left the White House in September this year amid a dispute over whether he resigned or was shown the door.

His name has been frequently raised in testimony in the impeachment inquiry, as a senior official apparently appalled by Trump’s moves to pressure Ukraine into investigating unfounded allegations of corruption against Joe Biden and his son Hunter and a baseless conspiracy theory which seeks to shift blame for Russian interference in the 2016 election.

The former Russia adviser Fiona Hill said Bolton characterised the attempts as a “drug deal” cooked up in part by Rudy Giuliani, Trump’s personal lawyer who she said Bolton called “a hand grenade that was going to blow everyone up”.

It has been reported that Bolton played a key role in freeing part of nearly $400m in security aid to Kyiv which was being held as bait. Furthermore, Bolton’s lawyer has said he has “personal knowledge” of meetings and conversations “that have not yet been discussed in testimonies thus far”.

But Bolton has nonetheless asked a judge to decide if he should comply with House Democrats and testify, a move largely seen as an effective means of delay.

Gordon Sondland, ambassador to the EU, remains the most senior Trump appointee to have testified – damningly for the president, most observers agreed.

Bolton has reportedly signed a book deal worth $2m, prompting suggestions that he intends to save his revelations for the commercial market.

On Friday Bolton returned to Twitter after a two-month silence, claiming to have “liberated” his account after it was “suppressed unfairly in the aftermath of my resignation”.

“The White House,” he claimed, “refused to return access to my personal Twitter account. Out of fear of what I may say? To those who speculated I went into hiding, I’m sorry to disappoint!”

He seemed to be enjoying trolling those who want him to speak to the House intelligence committee, claiming his tweets represented “full disclosure” and adding on Saturday: “The presidency and control of the House and the Senate will all be decided in less than one year. It’s time to speak up again!”