Newly released emails between the office of Mike Pompeo and NPR reporter Mary Louise Kelly cast further doubt on the secretary of state’s extraordinary claim that the journalist lied to him before a contentious interview.

Pompeo, who reportedly subjected Kelly to an expletive-ridden rant in his private living room after an interview during which he was asked about his role in the Ukraine scandal, issued a statement in which he accused the reporter of violating “the basic rules of journalism and decency”.

Kelly maintained that her meeting with Pompeo after the recorded interview was not agreed to be off the record.

NPR has stood by its reporter and emails quoted by the Washington Post show Kelly clearly expressing that Ukraine would be discussed.

Donald Trump weighed in over the weekend, questioning the legitimacy of the independent nonprofit media outlet, one of America’s most trusted news sources.

In a tweet on Sunday, Trump agreed with comments that labelled the station, which reaches 120 million monthly listeners, a “big-government, Democrat party propaganda operation” and asked: “Why does NPR still exist?”

“A very good question!” the president responded.

Pompeo was subjected to rigorous questioning on the administration’s handling of Iran and the Ukraine scandal last Friday by Kelly, a veteran foreign policy reporter. He grew audibly frustrated as the interview continued.

The secretary of state, at the centre of the scandal that has engulfed Trump’s presidency and led to his impeachment, was asked why he had not expressed support for the US ambassador to Ukraine, Marie Yovanovitch, who was ousted from her position as Trump pressed for investigations into his domestic political rivals.

The email exchanges obtained by the Post, between Kelly and Pompeo press aide Katie Martin, were sent a day before the interview and clearly show Pompeo’s office was told he should expect questions on the issue.

“Just wanted to touch base that we still intend to keep the interview to Iran tomorrow,” Martin stated. “Know you just got back from Tehran so we would like to stick to Iran as the topic as opposed to jumping around. Is that something we can agree to?”

Kelly replied: “I am indeed just back from Tehran and plan to start there. Also Ukraine. And who knows what the news gods will serve up overnight. I never agree to take anything off the table.”