'Panorama has gone independent republic on this. There are old scores being settled'

"And before the Top Gear special here on BBC2, some golden memories from the archives of a true TV legend, the late great Sir Jimmy Savile at the BBC… How's About That Then?"

These gushing words were broadcast on 28 December last year before a glowing tribute to the late Jim'll Fix It host – a programme broadcast 26 days after George Entwistle, who had responsibility for the show, had been informed by the BBC's director of news, Helen Boaden, that Newsnight had undertaken an investigation into the presenter – and that this might create scheduling problems.

Today, Mr Entwistle, now the Corporation's Director-General, will give evidence to Parliament about why he chose not to dig deeper into Newsnight's evidence before he gave the Savile tribute the go-ahead.

Mr Entwistle's appearance before the Commons Select Committee on Culture, Media and Sport comes as the Corporation tears itself apart in a way that was unimaginable when the BBC careerist began his job barely a month ago. Internecine battles are breaking out around the organisation.

Last night, BBC1's investigative flagship, Panorama, broadcast the damning documentary about the editorial failings at Newsnight, the chief current-affairs show on BBC2, with one editorial insider commenting: "There is no love lost between the programmes; Panorama has always been quite aggressively competitive."

What began last year as a Newsnight investigation into the alleged criminal activities of a celebrity figure from a bygone era has turned into a Panorama probe into Newsnight and the current senior management of the BBC.

"Panorama has gone completely independent republic on this and there are probably some old scores being settled," a source said. Blogs and tweets from current and former BBC journalists have taken opposing stances.

Already, Peter Rippon, the editor of Newsnight, has been obliged to stand aside after BBC executives decided his account of why he dropped an investigation into Savile last December was lacking credibility.

The BBC Trust, led by Lord Patten, says it is "deeply concerning" that the BBC – i.e. Mr Rippon – produced an inaccurate version of what happened. And the turn of events – caused by leaked emails written by Newsnight journalists angry at the way their investigation was being misrepresented, which were published in this newspaper and also obtained by Newsnight, – has raised questions about Lord Patten's handling of the affair.

On Radio 4's The Media Show on 10 October, the peer made a staunch defence of Mr Rippon's reputation and of Mr Entwistle's reluctance as director of BBC Vision to find out about the Newsnight evidence. "If you press the point, it then starts to look as if you are trying to interfere with the programme and stop it being shown," the chairman of the BBC Trust said.

Ms Boaden is also under pressure: MPs will today gauge the strength of her warning to Mr Entwistle on 2 December when she raised concerns about the scheduling of the Savile programmes. The director of news has been obliged to absent herself from the BBC's coverage of the story while an internal investigation takes place into why Newsnight's piece was dropped.

The corporate team at the BBC's communications department have also had to respond to damaging allegations released to the media by their own colleagues who were publicising last night's Panorama.

Since the Hutton Inquiry in 2003, the previous Director-General, Mark Thompson – whom Ms Boaden also spoke to about the Savile scheduling in 2011 – was supposed to have put in place a management structure and editorial culture that would prevent another BBC meltdown. But Mr Thompson's successor is clinging to his job just 37 days into his tenure, and is learning to his cost that the BBC system is still fallible.