BBC announced the beginning of an investigation into how it obtained an explosive 1995 interview with Princess Diana that mentioned her marital issues with Prince Charles.
It had approved the appointment of former Supreme Court judge John Dyson to lead the probe.
The interview was aired in November 1995 where she spoke about the collapsing marriage with Charles due to his long-time lover Camilla Parker-Bowles.
Watched by a record 22.8 million people, Diana said that she was also unfaithful.
The interview was conducted by reporter Martin Bashir.
Late princess's brother Charles Spencer alleged that Bashir showed him fake documents to persuade his sister to take part.
Bashir used underhand methods to persuade Diana to talk, including by claiming her own staff members were paid to spy on her.
Dyson called this an important investigation.
Diana and Charles divorced in 1996 but the following year saw her death in a car crash.
Martin Bashir previously faced a similar controversy over a Michael Jackson documentary where Jackson admitted to sleeping with children.
The documentary conjured the investigations into child sexual abuse by Jackson, leading to trial in court.