Earl Spencer has said he is “not at all satisfied” with the parameters of an inquiry into the BBC Panorama controversy surrounding the interview with his sister Diana, Princess of Wales.

He has previously alleged he was shown “false bank statements” by interviewer Martin Bashir ahead of Diana’s interview with Panorama, and they were used to help the reporter gain access to the princess.

The broadcaster has appointed a retired judge, Lord Dyson, former master of the rolls, to lead an investigation into the Diana interview.

But on Friday, Earl Spencer questioned the scope of the probe.

He tweeted: “As I’ve told the BBC this evening, I’m not at all satisfied with the parameters they’ve set around their enquiry into the @BBCPanorama interview with Diana of 25 years ago tonight.

“Lord Dyson must be free to examine every aspect of this matter, from 1995 to today, as he sees fit.”

The BBC has insisted that investigation has a sufficiently broad scope.

A spokesman for the corporation said: “The review is fully independent and the terms are suitably broad and wide-ranging.

“We hope that everyone will support Lord Dyson’s work in establishing the truth.”

The investigation will consider if the steps taken by the BBC and Bashir were appropriate and to what extent those actions influenced Diana’s decision to give an interview.

It will also examine what knowledge the BBC had in 1995 and 1996 of “mocked up bank statements purporting to show payments to a former employee of Earl Spencer (and) the purported payments to members of the Royal Households”, the corporation said.

The explosive Panorama interview famously featured Diana saying: “Well, there were three of us in this marriage, so it was a bit crowded.”

The BBC says Diana had written a note saying she did not see the false bank statements and they played no part in her decision to give the interview.

On Thursday, TV watchdog Ofcom said it will not launch its own investigation into the BBC Panorama controversy, but will follow the independent inquiry “closely”.

The Duke of Cambridge has previously welcomed the investigation, saying it “should help establish the truth behind the actions” that led to the programme.

The BBC said Bashir, who is now its religion editor, is currently signed off from work, recovering from quadruple heart bypass surgery and with significant complications from having contracted Covid-19 earlier in the year.

The princess sent shockwaves through the monarchy with the interview, which included candid details about her marriage and the Prince of Wales’s rumoured relationship with Camilla Parker Bowles, his now wife.

Diana also questioned Charles’s suitability as king.

A month later, the Queen urged the separated couple to divorce, which they did in 1996. The princess died in 1997 in a car crash in Paris.