The Westminster Abbey event, which is being developed by BBC Studios Events Productions, was due to be hosted by the BBC but the show has been switched to ITV.
It comes after a Royal row over a BBC Two documentary examining the Duke of Cambridge and the Duke of Sussex’s relationship with the media.
A rare joint statement last week from all three Royal households - Buckingham Palace, Clarence House and Kensington Palace, criticised The Princes And The Press.
The Royal households said the broadcaster had given "credibility" to “overblown and unfounded claims”.
It is not known whether the switch was linked to the documentary, but ITV sources told Royal Editor Chris Ship they were only made aware of the offer less than two weeks ago, with one source saying: “It was unusual for it to come to us this late.”
ITV said the carol service, hosted by Kate and supported by the Royal Foundation, would recognise and celebrate the work of “individuals and organisations across the nation who have stepped up to support their communities through the pandemic”.
The event, which will be broadcasted on Wednesday December 8, will see the Westminster Abbey choir deliver carols, alongside readings and musical performances by a variety of guests.
Guests will range from those involved in grassroots community projects, charity workers and volunteers, to teachers, emergency responders and armed forces personnel, ITV said.
The audience will also feature people who have gone “above and beyond” to care for and protect others during the last 18 months, including those working in roles relating to mental health, families and early development.
A statement from William and Kate on the social media accounts of Kensington Palace confirmed the news, writing: "This Christmas we are celebrating the incredible work of individuals and organisations across the nation who go above and beyond to support their communities.
“Next week, the duchess will host a Christmas carol service at Westminster Abbey, supported by The Royal Foundation, bringing many of those inspirational people together.
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“The service, which will be broadcast in December, will look back on the last 18 months, to think not only of the unprecedented challenges that we have all faced as we continue to navigate the Covid-19 pandemic, but also to remember the positives: people and organisations pulling together in their communities, the small acts of kindness across different demographics and generations, and the unsung heroes who stepped up to help others.”
The two-part BBC documentary The Princes And The Press, presented by Amol Rajan, included suggestions negative stories about the Duchess of Sussex were leaked by courtiers and there was a competitiveness between households.
It also saw a private investigator reveal the extent of his surveillance on the private lives of Prince Harry’s girlfriends for the now-defunct News of The World paper.
Buckingham Palace, Clarence House and Kensington Palace took the rare step of issuing a joint statement to the broadcaster which was included at the end of the documentary.
The statement from the palaces said: “A free, responsible and open press is of vital importance to a healthy democracy.
“However, too often it is overblown and unfounded claims from unnamed sources that are presented as facts and it is disappointing when anyone, including the BBC, gives them credibility.”