Veteran investigative journalist joins a growing chorus of criticism of the public service broadcaster.

As the BBC reported on Boris Johnson’s “gut instinct” that jam precedes cream on scones, its former investigative journalist John Sweeney said the corporation has failed to tell “truth to power about Brexit” and its director general should resign.

The award-winning reporter was discussing whether journalism is resulting in fundamental structural change at London’s Frontline Club last night, as questions were again being asked about the BBC’s judgement in airing interviews by Andrew Neil with Nicola Sturgeon and Jeremy Corbyn – despite Johnson having yet agreed to the same ritual.

“Brexit is a dark fairy story and the BBC, this great and wonderful institution, hasn’t told truth to power about Brexit,” Sweeney said.

There is a problem with Tony Hall because he’s not brave enough… he should go. John Sweeney

Having left the BBC this year after being secretly filmed by a supporter of Stephen Yaxley-lennon while he was working on a Panorama documentary – not yet broadcast – on the right-wing figure known as ‘Tommy Robinson’, Sweeney said he was deeply concerned by the “lack of courage” by those at the top of the institution, which is resulting in Johnson being given an easier ride than others.

“[The BBC] did a very tough film about Jeremy Corbyn and anti-Semitism, but there hasn’t been a programme about Boris and the Russians and that worries me,” he said. “I think, at the moment, the BBC leadership – and I’m thinking in particular of Tony Hall – is too fearful and he has no courage, none at all, and he should go.”

Rather than boldly informing its audiences on issues of public importance, the corporation is not brave enough and is merely responding to public pressure here and there, he said – pointing to the example of the BBC Breakfast presenter Naga Munchetty being found to have breached the corporation’s guidelines by criticising Donald Trump’s call for four Congresswomen of colour to “go back” to where they came from. Hall reversed the decision after a public backlash, telling BBC reporters that “racism is not an opinion and it is not a matter for debate”.

Sweeney said: “Naga Munchetty, who’s brilliant, she reacts in a perfectly human way… Under pressure, the BBC changes its mind. Then the other day, I understand that it’s not seemly to have the audience laughing at Boris when he’s saying ‘trust me, I’m an honest guy’, and they defended [the editing of a news clip to omit the laughter] for two days and then the BBC, under pressure, switches.

“So, I think there is a problem with Tony Hall because he’s not brave enough for the job and the BBC is a precious thing.”

Sweeney’s last few years at the BBC were characterised, he said, by travelling to Leave-voting towns where he would head to the “market square” to get the opinion of a Leave voter, then to a “Waitrose” to speak to a Remainer – rather than spending time investigating the likes of Arron Banks and Nigel Farage.

But, stories properly scrutinising populist politicians, their motives and interests are not as significant to audiences as they once were, he acknowledged.

“What’s happened is there is a new zeitgeist which is, if you’re populist – like Boris Johnson talks about ‘letterboxes’, or Salvini and the terrible things he says about Roma or Gypsies, or Trump – you can’t get traction [with a story about this]. There is a problem that what used to really upset and anger people and cause for change to happen is no longer working and it’s part of the deconstruction of the kind of civilised conversation, democratic conversation, that I’ve been used to my entire life.”

In response to a letter by Sweeney to the broadcasting regulator Ofcom about his concerns that the BBC is not covering certain stories, the public service broadcaster pointed to the impact of its recent Newsnight interview with Prince Andrew, exploring his relationship with the sex offender Jeffrey Epstein, among other examples. The royal controversy is a story that is being followed up by the BBC, with an hour-long Panorama investigation set to air on Monday.

But, the question is: why isn’t this same level of scrutiny being applied to Boris Johnson who, unlike Prince Andrew, could soon be an elected Prime Minister, capable of affecting the lives of millions of people living in this country?

Alongside Emily Maitlis’ forensic questioning of Prince Andrew and Andrew Neil’s interrogation of Jeremy Corbyn – both in the public interest and the proper function of journalists – where is the robust challenging required of Boris Johnson? What about his lies (which the BBC won’t say make him a liar), the electoral wrongdoing of his Vote Leave campaign, his Russian connections, his hedge fund funding, and his lack of policies for Britain beyond his disingenuous “Get Brexit Done”?

While the Prince Andrew affair has certainly shaken the monarchy, arguably the bigger crisis for its constitutional role this year came with Johnson’s unlawful prorogation of Parliament and misleading of the Queen. As Anthony Barnett has written in these pages, it exposed Elizabeth II as the “hollow heart” of the British Constitution. Will Johnson be asked to explain any of this? Not a chance.

The BBC will let him eat scones.