Republican shadow chancellor John McDonnell has backed the publicly funded £370 million restoration of Buckingham Palace and suggested he kneeled before the Queen at a recent official ceremony.
The Labour left-winger declared the Queen's main residence a "national monument" and said no government would allow it to fall into disrepair.
And he indicated that when he was recently inducted into the Privy Council he kneeled before the monarch, despite previous suggestions that he would not.
On Buckingham Palace, Mr McDonnell told Matt Frei on LBC radio: "It's a national monument...national heritage, it's going to be treated that way, in the same way as the House of Commons.
"When you have these old buildings they have to be looked after."
Asked if the Queen should pay for the work, instead of the money coming from a 66% increase in the Sovereign Grant, he said: "She may well consider that.
"I am a republican but when it comes to decisions like that I think they are left to her."
As a member of the Privy Council, Mr McDonnell is now entitled to be referred to as "Right Honourable" and receive top secret national security briefings.
Asked if he got down on "bended knee", he replied: "I did the usual protocols."
"I think you're not supposed to talk about what happens... I'm not sure what the rules are. You can say I did the usual protocol - not far distant from the one you're suggesting."
Labour leader, and fellow republican, Jeremy Corbyn said after he joined the Privy Council last year: "We shook hands like two adults", when asked if he had knelt before the Queen.