Channel 4 News has said that Downing Street froze it out of a planned interview at the G7 summit because of criticism of Boris Johnson by the channel’s head of news, who had described him as a “known liar” and a “coward”.

According to the editor of Channel 4 News, Ben de Pear, a team of journalists had flown to Biarritz after being invited but Downing Street advisers then said Dorothy Byrne’s criticism of the prime minister had resulted in access being denied.

He added that the programme was “looking for clarity” after Johnson was said to have suggested the lack of access was due to a shortage of time.

The row follows a warning last week by Byrne, Channel 4’s head of news and current affairs, that politicians including Johnson and Jeremy Corbyn were adopting the tactics of Donald Trump by declining to appear on major news programmes to subject themselves to scrutiny.

In a speech at the Edinburgh television festival, she asked: “Here is what we all need to decide: what do we do when a known liar becomes our prime minister?”

The Channel 4 news Twitter account said a planned interview with Johnson, who spoke on Sunday to a range of media outlets including the BBC and ITV on the fringes of the summit in the French city, had been cancelled, despite the team being told to travel to the summit for the interview.

“Decision by @10DowningStreet was made following criticism from Dorothy Byrne that Mr Johnson limits access to media like Putin,” it stated.

It added that No 10’s reasons for the cancellation had varied, with one senior adviser saying the interview was scrapped because of Byrne’s speech.

Downing Street sources have briefed that they were unhappy about the Byrne speech at the Edinburgh television festival, but decided not to take action.

However, the same sources said an interview Byrne gave to Sky News afterwards crossed the line of impartiality for a broadcaster. Attempts were also made to brush off the idea the prime minister was evading scrutiny, with Downing Street pointing out that he had granted interviews to a range of other broadcasters.

Johnson himself was tackled about the issue by ITV’s political editor, who suggested that the prime minister had “shot himself in the foot” in the response to Byrne’s critique. Johnson sidestepped the specific issue around the Channel 4 interview, insisting he had been speaking to lots of other media.

It was unclear which specific comments No 10 took umbrage against. In her interview with Sky News, Byrne said: “That L word isn’t a word that I would bandy about but I think that when we are divided the one thing that we must unite on is the central importance of truth.”

“In the US it has started to be that a number of political figures have said that each person’s truth is just a matter of their own opinion, there is no such thing as truth,” she said.

“What I am saying is that we mustn’t go down that road. This is in many ways a warning to politicians that you have got to tell the truth and if you do not we will call you out. If so, keep your own house in order. It’s not about me being against any particular politicians.”