LONDON — A British television channel defied royal wishes and said yesterday it plans to show photographs taken immediately after the car crash that killed Princess Diana.Diana’s sons, Prince William and Prince Harry, had protested that showing the photographs would be a “gross disrespect to their mother’s memory.”

“If it were your or my mother dying in that tunnel, would we want the scene broadcast to the nation?” the princes’ private secretary, Jamie Lowther-Pinkerton, said in a letter to Channel 4 television.

The documentary, “Diana: The Witness in the Tunnel,” is scheduled for broadcast Wednesday at 9 p.m. The princess and her friend Dodi Fayed died along with their chauffeur in a car crash in Paris on August 31, 1997.

“We have weighed the Princes’ concerns against the legitimate public interest we believe there is in the subject of this documentary and in the still photography it includes,” said Julian Bellamy, head of Channel 4.

The broadcaster said the documentary focused on the role of the photographers at before and after the crash.

“Did the photographers chase Diana to her death in the Pont d’Alma tunnel?” the company’s website said. “Were they too busy taking pictures to call the emergency services and did their presence hinder those services?”

Lowther-Pinkerton’s letter acknowledged that William and Harry had not been allowed to see the documentary, but the secretary had seen it and had briefed the princes on the contents.

Channel 4 said some of the photographs were taken by professionals and others by passers-by. The documentary focuses on the photographers who were arrested on the night.

“In publishing the letter, the princes reluctantly feel that they have been left no choice but to make it clear publicly that they believe the broadcast of these photographs to be wholly inappropriate, deeply distressing to them and to the relatives of the others who died that night, and a gross disrespect to their mother’s memory,” said a statement issued by Clarence House, official residence of the princes and their father, Prince Charles.

Channel 4 defended the documentary as “a well-made and responsible documentary.”

“These photographs are an important and accurate eyewitness record of how events unfolded after the crash.

“We acknowledge that there is great public sensitivity surrounding pictures of the victims and these have not been included. Some photographs will be of the scene inside the tunnel but in none of the pictures is it possible to identify Diana or indeed any of the crash victims.

“We do not show, nor have we ever considered showing, Diana’s final moments.”

Lowther-Pinkerton, however, said the photos “are redolent with the atmosphere and tragedy of the closing moments of her life.”

“As such, they will cause the princes acute distress if they are shown to a public audience, not just for themselves, but also on their mother’s behalf, in the sense of intruding upon the privacy and dignity of her last minutes,” he wrote.