The Prince of York says he is withdrawing from royal duties because the scandal of Jeffrey Epstein has become a "serious disorder" for the royal family.
Prince Andrzej said he had asked the Queen for permission to withdraw in the "foreseeable future."
He said he deeply sympathized with the victims of Epstein's sex offender and everyone who "wants some form of confinement."
The prince met with a growing reaction after an interview with the BBC about his friendship with the American financier Epstein.
In a statement he said: "I still regret my misjudged relationship with Jeffrey Epstein.
"His suicide has left many unanswered questions, especially for his victims, and I deeply sympathize with everyone who has been touched and wants some form of confinement.
"I can only hope that in time they will be able to rebuild their lives."
He added that "he is ready to assist any relevant law enforcement authorities in their investigations, if required."
Earlier, a letter written to the Times newspaper by Buckingham Palace questioned when the prince met Epstein for the first time.
A 2011 letter says they met in the early 1990s, not in 1999, as Prince Andrew said in an interview with the BBC.
The letter was published after the Times reported the existence of a photo of a prince with 17-year-old Virginia Giuffre, then known as Roberts, who later testified that she was forced to have sex with him.
The prince has always denied any form of sexual contact or relationship with her.
In an interview with the BBC in Newsnight on Saturday, the prince said he met Epstein, "he met his girlfriend in 1999" – a reference to Ghislaine Maxwell, who had been a friend of Prince Andrew since she was at university.
The prince said he did not remember ever meeting Mrs Giuffre, and remembered that he had gone to Pizza Express in Woking and then returned home the night he claimed they had met.
He tried to undermine her testimony that he was "sweating profusely" in a nightclub, saying that his health at the time meant he couldn't sweat.
And the prince said that the last meeting of Epstein in 2010 was a "bad decision," but said that "the opportunities I was given to learn" about business means that he doesn't regret friendship.
BT has become the latest in a series of organizations that have distanced themselves from Prince Andrew after this interview.
In a statement, the company said it was working with iDEA – which has been helping people develop digital, business and employment skills – since 2017, but "our relationship was with executive directors, not its patron, Prince of York."
"In the light of recent changes, we review our relationship with the organization and hope that we will be able to continue working with them if their patronage changes," said a spokeswoman.
Standard Chartered Bank and KPMG also announced that they are withdrawing support for Prince Pitch @ Palace's business mentoring initiative. Sources informed the BBC that decisions had been taken prior to the interview.
Four Australian universities have also stated that they will not continue their involvement in Pitch @ Palace Australia.
In September, three days after the interview was broadcast, Prince Andrew canceled a planned visit to areas flooded by the Yorkshire flood.