Donald Trump’s White House asked the Pentagon to play down and delay reports of brain injuries suffered by US troops from an Iranian missile attack on Iraq last year, according to a former defense spokeswoman.

Alyssa Farah said she fended off the pressure from the White House, which came after Trump had first claimed there had been no casualties and then dismissed the injuries as “headaches” and “not very serious”.

More than 100 US troops were ultimately diagnosed as having suffered traumatic brain injuries in the missile attack on two bases in Iraq housing US troops on 8 January 2020, launched by Tehran in retaliation for the US drone killing of Revolutionary Guard general Qassem Suleimani five days earlier.

Roughly 80% of the American casualties from the missile attack were able to return to duty within days, but dozens had to be evacuated to Germany and then the US for treatment.

Farah described the attack as the “heaviest several hours of my life” in an interview with a new podcast, One Decision, hosted by former CNN journalist Michelle Kosinski and the former head of Britain’s MI6 intelligence agency, Sir Richard Dearlove.

Farah, who went on to work in the White House, said that when Trump claimed there had been no casualties in the wake of the attack it was “true at the time that we gave those facts to the president”.

But she added: “I think where things got shaky was there was an effort from the White House to want to say, this was not successful – the Iranians were not successful in harming our targets in response. And I think that went too far.

“And I think that it ended up glossing over what ended up being very significant injuries on US troops after the fact,” Farah told the podcast, due to air on Thursday.

She said it was Pentagon policy to release the facts as they arrived and were verified, and as a result the total reported number of casualties climbed throughout January 2020, irritating the White House.

“We did get pushback from the White House of, ‘Can you guys report this differently? Can it be every 10 days or two weeks, or we do a wrap-up after the fact?’” Farah said. “The White House would prefer if we did not give regular updates on it. It was this drip, drip of quote unquote bad news.”

Farah said she did not give in to the pressure, saying: “My feeling was, if my experience had taught me anything, transparency is always going to be your best friend in that field.”

The killing of Suleimani, as his car was leaving Baghdad airport on his arrival in Iraq on 3 January 2020, was highly controversial. The UN’s special rapporteur on extrajudicial killings at the time, Agnes Callamard, deemed it an “unlawful killing” because Washington had not provided sufficient evidence of an imminent threat from Suleimani.

Four days before the air strike a mob of Shia militiamen and their supporters breached the compound of the US embassy in Baghdad before being persuaded to withdraw. After Suleimani was killed the then US secretary of state, Mike Pompeo, claimed there was evidence Suleimani was planning an “imminent” attack against US embassies and bases, and Trump said later there was a plot “to blow up our embassy”. But members of Congress said there was no such claim in their intelligence briefing on the drone strike. Pompeo later said the strike was aimed at “deterrence”.

Farah insisted there was “extremely credible, thoroughly planned potential to harm US and coalition partners”.

“The ‘imminence’ is really the word that I think folks would get hung up on how immediate it was,” she added. Farah said she advised the top officials at the Pentagon not to base the justification solely on the claim of imminent attacks but because “we had a terrorist on the battlefield in Iraq and an extremely bold thing for this leader to be doing, watching the Green Zone be attacked from the ground in Iraq”.

US legal opinion is divided on the Suleimani strike. Some scholars said it was justified by the Iranian general’s role across the region of orchestrating attacks on the US and its allies. Others argue that does not provide sufficient cause under international law, because there was no declared state of war between the US and Iran.

“I believe that it was in violation of international law because we were not at war with Iran,” said Gary Solis, a retired marine, former adjunct professor at West Point military academy, and author of 2006 book the Law of Armed Conflict. “Not only were we not at war with Iran, but where we killed him was in a state with which we are not at war. So what authority did we have to kill him?”