He added that Kate has “shown tremendous bravery” and wished her “a speedy recovery”.

The Princess of Wales confirmed she is undergoing chemotherapy for canacer but did not say which type of cancer she has been diagnosed with.

Sunak wrote: “My thoughts are with the Princess of Wales, Prince of Wales, the Royal Family and in particular her three children at this difficult time. The Princess of Wales has the love and support of the whole country as she continues her recovery.

“She has shown tremendous bravery with her statement today. In recent weeks she has been subjected to intense scrutiny and has been unfairly treated by certain sections of the media around the world and on social media.

“When it comes to matters of health, like everyone else, she must be afforded the privacy to focus on her treatment and be with her loving family.

“I know I speak for the whole country in wishing her a full and speedy recovery and look forward to seeing her back in action when she’s ready.”

Starmer added that his “thoughts are with the whole Royal Family as they come to terms with the news”.

He wrote: “On behalf of the whole Labour Party, I want to send my very best wishes to Her Royal Highness at this distressing time.

“Our thoughts are with the whole Royal Family as they come to terms with the news and as they support The Princess of Wales through her treatment and recovery.

“Any cancer diagnosis is shocking. But I can only imagine the added stress of receiving that news amid the lurid speculation we’ve seen in recent weeks.

“Their Royal Highnesses are entitled to privacy and, like any parents, will have waited to choose the right moment to tell their children.

“I am heartened by The Princess of Wales’ optimistic tone and her message of faith and hope. Her Royal Highness will be in our thoughts and prayers as she progresses through her treatment with the love and support of not just her whole family, but the whole nation too.”

Former Home Secretary Suella Braverman also shared her best wishes for the Princess.

She wrote: “On behalf of the people of Fareham, I wish HRH The Princess of Wales a swift recovery as she undergoes treatment for cancer. Sending prayers and love.”