Boris Johnson is a “known liar” who is copying Vladimir Putin’s approach to the media, according to Channel 4’s head of news and current affairs, who called on broadcasters to aggressively challenge the prime minister’s falsehoods.

Dorothy Byrne said Johnson’s shift towards publishing his own videos on Facebook rather than giving sit-down interviews to journalists reminded her of the Russian president, “who also likes to talk directly to the nation”.

She also said television producers should be more willing to directly accuse political leaders of lying. “If we continue to be so polite, how will our viewers know that politicians are lying?” Byrne asked.

The comments are likely to increase tensions between Downing Street and Channel 4, with No 10 already discussing whether it benefits the government to engage with some traditional media outlets. Johnson has declined to be interviewed by the broadcaster in recent months and did not take part in Channel 4’s Conservative leadership debate, with his aides casting doubt on its impartiality.

Byrne was speaking during Edinburgh television festival’s annual MacTaggart lecture – seen as one of the British TV industry’s most important events – in which she accused prominent television figures of sexual harassment.

Byrne also used her speech to call out Johnson’s strategy chief, Dominic Cummings, describing him as “the UK’s most famous recipient of EU farming subsidies”, while criticising a number of Vote Leave claims about the supposed benefits of Brexit.

Byrne said it was time for the television industry to collectively demand politicians give proper interviews, suggesting Johnson was copying the tactics of “Mr Chlorinated Chicken himself, Donald Trump”.

She said she found the experience of listening to Radio 4’s Today programme to be like “accidentally walking into a knitting shop in Bournemouth”, but leading politicians had a duty to appear on the programme to explain their decisions. “Boris Johnson and Jeremy Corbyn are cowards … If they really believe in the policies they promote, they should come on to television to explain them, to allow them to be scrutinised and to justify them,” Byrne said.

Byrne, who described herself as the “oldest female TV executive working for a broadcaster”, also highlighted the historically high level of sexual assault in the industry and said the list of individuals who had previously delivered the MacTaggart lecture contained a man “who has not yet had the comeuppance he deserves for his assaults on women”.

In one anecdote, Byrne highlighted how the television industry was still not welcoming to middle-aged women and said there needed to be more awareness of flexible working for people going through the menopause – citing an incident involving Kevin Lygo, who is now ITV’s director of television.

“We were meeting one day when he suddenly remarked that I looked seriously unwell. I said I was not ill. ‘But you’ve gone all red and you seem to have a fever,’ he said. I repeated, ‘I am not ill, Kevin,’ in what I thought was a meaningful way. He repeated that I was and I should go home. So I went back to my desk and announced I was leaving for the day. Everyone asked me why and I said: ‘Because my boss has never heard of the menopause,’” she said.