Prince Charles refused to provide a formal witness statement to the child sex abuse inquiry, lawyers told a hearing on Monday.
The inquiry is currently hearing evidence relating to abuse carried out by Peter Ball, the former bishop of Lewes and of Gloucester, who knew the prince and exchanged letters with him.
Lawyers for the Prince of Wales used human rights law to object to block efforts to compel him to send a witness statement in the format used by the inquiry, instead sending a signed letter.
Fiona Scolding, lead counsel to the investigation into the Anglican church, said that his lawyers had previously argued that compelling him to give evidence was outside its powers.
Ball was convicted in 2015 of misconduct in public office after admitting abusing 18 teenagers and young men between the 1970s and 1990s.
His abuse had first been reported to the church in 1992, but police and CPS decided to give him a caution, and he was stripped of his role as bishop.
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He was later allowed to officiate at events including at schools and confirmations.
Ms Scolding said there would have been "no doubt" about what the inquiry's lawyers were asking for, as they sent a template for the document and used the word "statement" five times in one letter asking for the document to be signed.
"Despite lengthy correspondence, including assertions from the Prince's solicitors that the Inquiry's requests for evidence were outside its powers, i.e. 'ultra vires', there was never any suggestion at any point that the statement would be provided by letter," she said.
The inquiry made several attempts to compel the lawyers to provide a witness statement with a formal statement of truth, which is essentially equivalent to swearing on oath.
The prince's law firm Harbottle & Lewis also tried to argue that asking for a witness statement was "unfair", and constituted a request for "intensely private and confidential" personal data.
"This will inevitably raise concerns that the letter may be less than entirely frank about his relationship with Peter Ball and that it contains matters to which he is reluctant to attach a formal statement of truth."
Following "lengthy and extensive correspondence" an agreement was reached and the inquiry has decided to treat the letter, which ends with a sentence saying that its contents are true, as equivalent to a witness statement, she said.
The Prince will not give evidence in person but will have the statement read out at the hearing on Friday.
Earlier in the hearing Richard Scorer, of law firm Slater and Gordon, who is representing victims and survivors, expressed "surprise and concern" at the decision.
"This will inevitably raise concerns that the letter may be less than entirely frank about his relationship with Peter Ball and that it contains matters to which he is reluctant to attach a formal statement of truth," he said.
The prince's statement is expected to say that he was "not aware at the time of the significance or impact of the caution that Peter Ball had accepted", including the fact that a caution involves admission of guilt.
On Tuesday the Inquiry is expected to hear evidence in person from former Archbishop of Canterbury Lord Carey, who was found in an independent inquiry last year to be among senior church figures who "colluded" with Peter Ball.
Earlier in the day the inquiry heard that the church was dealing with a "turbulent" period in 1992, with Lord Carey raising the "constitutional crisis" caused by the Prince's split with Diana, Princess of Wales, as well as the decision to allow women to be priests.
William Chapman, a lawyer from Switalskis, also representing victims and survivors, told the inquiry that there had been concern that gay clergymen would be outed by a full criminal investigation, ending their career in the church.
A Clarence House spokesman said: "The prince made it clear that he was willing to help the Inquiry and voluntarily answered all the questions asked in the form of 'free flowing text' as requested by the Inquiry itself.
"The final submission includes a statement of truth in common with all witness statements. The legal exchanges, which have been extensively referred to by the Inquiry's solicitors, were necessary to ensure clarity regarding both the structure, relevance and content of the statement.
"Once resolved, the Inquiry raised no objection to the format of the prince's submission."