Labour leader Jeremy Corbyn. Reuters A media ethics watchdog group says the BBC's “clear and consistent bias” against the Labour leader in its news coverage is so bad it is considering taking legal action against the broadcaster.

Press campaign group the Media Reform Coalition (MRC) published a study in July, which found BBC news bulletins gave twice as much airtime to Corbyn’s critics than his supporters during the Labour leadership coup in June.

It presented the findings to the BBC, but has been disappointed with its lack of engagement since.

The group — which is made up of academics, media campaigners, and civil society groups — is now considering whether to take the corporation to court to uphold its legal duty to impartiality.

The BBC's royal charter and operating agreement set out its "regulatory obligation" to impartiality. It says: "The BBC must do all it can to ensure that controversial subjects are treated with due accuracy and impartiality in all relevant output."

Separately, Corbyn's former head of media Kevin Slocombe told Business Insider that the BBC was "not as fair" in its coverage of the Labour leader as ITV and Sky News. He said Corbyn's team had several high-level meetings with BBC News executives in an attempt to resolve the issue.

Slocombe made the comments to Business Insider as part of a detailed analysis of Corbyn's approach to media. Read the inside story of Jeremy Corbyn’s terrible relationship with the mainstream media.

A BBC spokeswoman said: "We are confident our coverage of Labour’s unprecedented, en masse frontbench resignation was impartial and we continue to air views from both sides of the party’s ongoing divisions."

Media Reform Coalition graph shows how "BBC News at Six" gave double the airtime to Corbyn's critics during the leadership coup. The left axis is the number of seconds given over to critics and supporters. Media Reform Coalition

The MRC analysed 40 prime time news bulletins from the BBC and ITV across 10 days. It found that the BBC gave over double the airtime to Corbyn's critics than it did to supporters, and overwhelmingly focused on negative issues for the Labour leader. By contrast, ITV gave a slim majority of its coverage to Corbyn supporters.

Justin Schlosberg, the director of postgraduate journalism at Birkbeck, University of London and MRC's chair, oversaw the study. He has been shocked by its "wholly inadequate" reluctance to engage with the findings.

It is BBC policy not to respond to outside research, but the academic is writing to the BBC again this week to ensure that the study has been seen by director of news James Harding.

Schlosberg is also exploring legal action. "We are looking at taking it to Ofcom and potentially even the courts. The BBC has to be held to account," he told us. "The BBC’s impartiality commitment is a legal commitment and so, I don’t know, it’s in the very embryonic stages of discussion. We will do whatever we can to make sure this issue is properly addressed by the BBC."

BBC insiders said the MRC study was limited in its scope, both in terms of the programmes analysed and the time frame it examined. They argued that it was natural for the news agenda to be led by the wave of MPs resigning from the shadow cabinet.

Former Corbyn press chief: BBC took too long to come to terms with changes in Labour party.

The findings resonated with Slocombe. He said news programmes such as "The Andrew Marr Show" and "Daily Politics," were very fair, but the BBC's news bulletins "took longer to come to terms with the shift in the direction of the Labour party."

He explains: "When Corbyn came in, it was a culture shock for all the broadcasters. All the contacts they had developed over the period of a decade had suddenly departed. They were suddenly on the back benches and not relevant in the leadership of the party. So all the broadcasters had to go and make new relationships. I think the BBC struggled with that and we had several high-level meetings when I was there, discussing coverage."

"The BBC were, on occasion on the news, happy to play up any crisis in the party more than ITV and Sky News," Slocombe added. "I wouldn’t say there was an agenda, it took them longer to come to terms with the shift in the direction of the Labour party."