The insider added: “William’s feeling is that the monarchy simply cannot survive mixed messaging when it comes to the York scandal and the damage it has done to public confidence.
“He believes there has to be a very visible and consistent separation between the institution and anyone connected to that fallout, even indirectly. From his perspective, allowing Beatrice and Eugenie to continue appearing at major royal occasions, mingling with senior royals and participating in prestigious public events risks blurring the boundaries the family has spent years trying to establish.
“He worries the public could begin to think the palace is quietly rehabilitating the Yorks by the back door, and that would undermine everything he is trying to build for the future of the Crown.”
Another source said Catherine, Princess of Wales, 44, strongly supports her husband’s position behind palace walls.
They added: “Kate’s position has hardened considerably over time because she believes the royal family can no longer afford to blur the line between personal compassion and public duty. Privately, she does feel for Beatrice and Eugenie and understands they are dealing with the consequences of decisions that were not their own, but she also feels the survival of the monarchy depends on maintaining credibility with the public.
“In her view, the institution has spent years trying to contain the reputational fallout surrounding Andrew, and bringing the sisters back into prominent royal events too visibly or too quickly risks dragging all of that controversy back into the spotlight again. Kate thinks the public expects consistency, and she fears any perception of leniency could seriously damage trust in the Crown.”