Earlier this week it was announced that the Queen would be taking part in the service leading the nation in commemorating the war dead.
The 95-year-old monarch has been under doctors’ orders to rest for almost a month.
However, she will no longer be attending after spraining her back.
Buckingham Palace confirmed that the Queen has sprained her back and will not attend the Remembrance Sunday service at the Cenotaph in London adding she is “disappointed” to miss the event.
It is understood the Queen has not received hospital treatment for her back and the injury is unrelated to recent medical advice for her to rest.
The Queen is said to regard the Remembrance Service at the Cenotaph as one of the most significant engagements of the year.
It is also understood she plans to continue with her schedule of light duties over the coming week.
In a statement, the palace said it was with “great regret” the Queen would be unable to attend the service.
The statement said: “The Queen, having sprained her back, has decided this morning with great regret that she will not be able to attend today’s Remembrance Sunday service at the Cenotaph. Her Majesty is disappointed that she will miss the service.
“As in previous years, a wreath will be laid on Her Majesty’s behalf by The Prince of Wales.
“His Royal Highness, along with the Duchess of Cornwall, the Duke and Duchess of Cambridge, the Earl and Countess of Wessex, the Princess Royal and Vice Admiral Sir Tim Laurence, the Duke and Duchess of Gloucester, the Duke of Kent and Princess Alexandra will be present at the Cenotaph today as planned.”
It is understood it is a recent sprain and there were concerns over the impact of a car journey and a period of standing on her recovery.
The Queen is said to be deeply disappointed over her absence and she will remain at Windsor Castle.
Alok Sharma, president of the UN Cop26 climate summit and former business secretary, wished the Queen “all the very best” after hearing she would be missing the Remembrance Day service in central London due to a sprained back.
Speaking to Sky News’ Trevor Phillips On Sunday programme, Mr Sharma said: “Obviously I’m very sorry to hear that, but I just got the news at the same time as you.
“As I understand it, this is precautionary and, of course, we wish Her Majesty all the very best.”
Baroness Scotland, the Commonwealth secretary-general, said there would be “sadness” that the Queen has had to pull out of attending the Remembrance Sunday service.
The peer said “everyone will be wishing her well” adding: “The Queen is adored, rightly. She has shown total commitment to the Commonwealth and she is much loved.
“I think there will be a lot of sadness but everyone will be wishing her well, everyone will want to see her again. She is the beating heart of most of the love that is in the Commonwealth, so we do wish her well.”