Prince William, Harry Rip BBC for 'Deceitful' Diana Interview in 1995

Prince William and his brother Prince Harry are finally on the same page about something -- condemning the BBC for the way it treated their mother ... specifically regarding her now infamous 1995 TV interview.

The Royal bros both made strong comments Thursday after an independent investigation into Princess Diana's explosive sit-down with BBC journalist Martin Bashir nearly 3 decades ago determined he and the network engaged in "deceitful behavior" and dishonest tactics to persuade her to do it.

William blasted the BBC, saying ... "the deceitful way the interview was obtained substantially influenced what my mother said," and he blames it for his parents' relationship falling apart.

He also added, "BBC’s failures contributed significantly to her fear, paranoia and isolation that I remember from those final years with her."

During the interview -- a huge get for Bashir and the BBC -- Diana notoriously stated that "there were three of us in this marriage" ... referring to Prince Charles’ relationship with Camilla Parker-Bowles, and her account of the marriage failing was watched by millions.

Prince Harry went further than his big bro, ripping not just the BBC, but British media in general and laying her death at their feet -- "The ripple effect of a culture of exploitation and unethical practices ultimately took her life."

He adds that he's deeply concerned that the practices used in 1995 are even worse, and more widespread, today.

As for what sparked the BBC inquiry -- Diana’s brother, Charles Spencer, recently accused Bashir of using false documents and trickery to gain access to the princess, and the retired judge who was appointed to handle the investigation confirmed those allegations were true.