The development comes after the Queen underwent tests in hospital last week and cancelled a two-day trip to Northern Ireland.
But the head of state has the “firm intention” of leading the nation in honouring the country’s war dead on Remembrance Sunday on November 14.
In a statement, Buckingham Palace said: “Following on from their recent advice that the Queen should rest for a few days, Her Majesty’s doctors have advised that she should continue to rest for at least the next two weeks.
“The doctors have advised that Her Majesty can continue to undertake light, desk-based duties during this time, including some virtual audiences, but not to undertake any official visits.
“Her Majesty regrets that this means she will be unable to attend the Festival of Remembrance on Saturday, November 13.
“However, it remains The Queen’s firm intention to be present for the National Service of Remembrance on Remembrance Sunday, on November 14.”
The 95-year-old monarch is said to be in good spirits, and during Friday afternoon recorded her Cop26 speech for the UN climate change conference which opens on Monday in Glasgow.
Earlier this week, the head of state announced she would not be attending the evening reception for world leaders on the global event’s opening day, and instead recorded the video message which will be played to delegates.
There will be concern for the Queen given her advanced years but medics see the period of rest as a sensible precaution.
The Queen appeared cheerful and in good humour when she hosted a virtual presentation ceremony on Thursday, awarding the Queen’s Gold Medal for Poetry 2020 to poet David Constantine.
Speaking from Windsor Castle during a video call, she joked with the writer at Buckingham Palace, saying about his award “Do you put it in a cupboard?
It was announced last Wednesday the Queen had “reluctantly” accepted medical advice to rest and cancelled her trip to Northern Ireland that was scheduled to begin that day.
Buckingham Palace confirmed the head of state had undergone “preliminary investigations” during her first overnight stay at a medical facility in eight years.