Weekly audiences between the King and Rishi Sunak are expected to resume in person in two weeks following Charles’ cancer diagnosis, it is understood.
Downing Street and Buckingham Palace took the unusual step of confirming details of a call between the two on Wednesday, in an attempt to show the King was carrying on with his duties.
The Prime Minister was due to wish Charles well in the brief phone conversation before formal face-to-face audiences are set to start again on February 21.
The King flew to his Norfolk residence, Sandringham, on Tuesday following a reunion with his son the Duke of Sussex at a meeting in London.
Asked if Mr Sunak would travel to Sandringham for his discussion with the King, the Prime Minister’s official spokesman said: “We don’t in general and we are not going to get into the habit of commenting on the PM’s conversations with the King.
“But we have agreed with the Palace in this specific instance to confirm that they will be speaking on the phone later.”
The King holds a private weekly audience with the Prime Minister to discuss Government matters.
Though the King is meant to remain politically neutral on all matters, he is able to “advise and warn” his ministers – including Mr Sunak – when necessary.
At Prime Minister’s Questions, Mr Sunak said: “I know the thoughts of the House and the country are with the King and his family.
“We wish His Majesty a speedy recovery and look forward to him resuming his public-facing duties in due course.”
Labour leader Sir Keir Starmer and SNP Westminster leader Stephen Flynn also expressed their support for the King.
Meanwhile, the Prince of Wales resumed public duties following his wife’s surgery and the King’s diagnosis.
William hosted an investiture ceremony at Windsor Castle and will attend a gala fundraising dinner for London’s Air Ambulance Charity.