The brother of Diana, Princess of Wales has used Twitter to criticise the BBC over its handling of an internal inquiry into his sister’s bombshell Panorama interview.

In a series of tweets, Earl Spencer said the corporation was “incapable of honestly facing up to the ugly truth of this matter”.

The BBC has said it will hold a new investigation into fresh allegations from Diana’s brother that he was shown “false bank statements” by BBC journalist Martin Bashir, to help him gain access to the princess.

But Charles Spencer reportedly wants an independent inquiry and has turned down the BBC’s offer to examine his claims, which he says are part of a dossier of new information surrounding the circumstances of Mr Bashir’s successful attempt to secure the interview with Diana.

The earl also accused former BBC director-general Lord Hall, who led the 1996 internal inquiry into whether his sister had been misled or not, of excluding him from that process.

Lord Hall, who at the time was the director of BBC news and current affairs, has told The Times newspaper he was “unaware” of the documents at the centre of the new claims.

In one tweet the earl suggested a reason why Lord Hall did not know about the documents: “This is hardly surprising: Hall chose to exclude me from the enquiry.”

He goes on to say in another post: “Answering the key question – why I was deliberately excluded from the enquiry (one I wasn’t even aware was being conducted) – has to be a part of an independent enquiry.

“The BBC has shown itself incapable of honestly facing up to the ugly truth of this matter.”

In his fresh claims the earl has said Mr Bashir showed him “false bank statements”, relating to alleged payments made to two members of the royal household by the security services, as he tried to gain access to Diana in 1995.

The suggestion being that the individuals were being paid for information about the princess.

Mr Bashir, now the BBC’s religion editor, is seriously ill with Covid-related complications and is not in a position to respond to the earl’s allegations, the BBC has said.

Charles told the Daily Mail: “I have declined the DG’s (director-general) offer of an internal BBC investigation, given how deeply concerning the 1996 one was to me, and I have told him I am going to seek an independent inquiry.”

The corporation’s 1996 internal inquiry examined claims Mr Bashir had used false financial documents, purporting to show a then member of the earl’s staff was leaking stories, as a way to persuade the princess to talk.

The BBC maintains there is a written note from Diana – although it no longer has a copy – attesting she had not seen the false bank statements for her brother’s then employee, and they played no part in her decision to give the interview.

The corporation has previously said in a statement that Mr Bashir admitted commissioning the mocked-up bank documents and it is understood the journalist was found to have “done wrong” at the end of the process, but it is not known what sanction, if any, he faced.

There is no suggestion any of the individuals that were the subject of any of the financial documents were involved in any wrongdoing.

In an earlier statement a BBC spokeswoman highlighted an apology the earl has received from director-general Tim Davie over the mocked-up documents relating to his former employee.

She said: “The BBC has apologised. We are happy to repeat that apology. And while this was a quarter of a century ago, we absolutely will investigate, robustly and fairly, substantive new information.

“We have asked Earl Spencer to share further information with the BBC.

“Unfortunately, we are hampered at the moment by the simple fact that we are unable to discuss any of this with Martin Bashir, as he is seriously unwell. When he is well, we will of course hold an investigation into these new issues.”