A debate has erupted over the future leadership of the Labour Party and journalism ethics after left-wing pundit Paul Mason was filmed criticising Jeremy Corbyn.

Mason, a former digital editor of Channel 4 News, has been an outspoken advocate for Corbyn during political rallies and TV appearances.

But a film obtained by The Sun newspaper appeared to show Mason claiming that the Islington North MP does not appeal to "the mainstream working class vote".

"Corbyn goes to England on a bike and cycles round. Working class people go to a leader," Mason reportedly told a confidante. "He has no cultural references to the way they live."

The commentator also tipped shadow business secretary Clive Lewis, 45, as a future leader.

"The person who I would replace Corbyn with eventually is this guy called Clive Lewis," Mason said.

Mason's private conversation was apparently recorded by a "bystander" in a Liverpool bar during Labour's annual conference.

The Independent Press Standards Organisation (Ipsos) code warns editors will be expected to "justify intrusions into any individual's private life without consent".

But media consultant David Banks told IBTimes UK the story "just" passes the public interest test.

"You have to a public interest justification for the intrusion on the conversation, and then the publication of what you find," he said.

"Mason is an interesting figure. He doesn't have a position in the Labour Party to my knowledge so it's not like this is a shadow minister, who is having this conversation who has previously declared allegiance to Corbyn. There you have a much clear cut [hypocrisy case].

Banks pointed out Mason is a "person of significance on the left", due to his media appearances, books and large social media presence. He has 300,000 followers on Twitter.

"He's not just an ordinary member of the public," Banks said. "I think he is an influential public figure on the Corbyn-wing of the left, therefore if he is having conversations [contrary to his support of the Labour leader] there is a public interest justification for what The Sun have done."

The video also raises the issue of subterfuge. The press must not seek to obtain or publish material acquired by using hidden cameras or clandestine listening devices, according to the Ipsos code.

But Banks argued the paper could make a public interest case on this point. "I don't think they would have got this information regarding Mason's views in any other way," he said.

"Simply going up to him and talking to him you wouldn't elucidate this answer from him.

"It's not an absolutely clear cut case...but I think [Mason] is sufficiently a public figure and he has made sufficient public statements in the past of a certain direction for this to justify an exposure of what it seems to show his views."

The Sun had not responded to a request for comment at the time of publication. IBTimes UK reached out to Mason over social media for comment.