The bearskin caps worn by soldiers outside Buckingham Palace now cost more than £2,000 each, figures from the Ministry of Defence (MoD) show.
The cost of the ceremonial caps, made from the fur of black bears, soared by 30% in a year, according to figures revealed in response to a Freedom of Information request from animal welfare campaigners.
The People for the Ethical Treatment of Animals (Peta) group are against using real fur in principle, but they say it is also now a financial as well as an ethical issue, with £1m spent on fur caps in recent years.
The MoD said: “We are open to exploring faux fur alternatives if they pass the necessary requirements."
However, the ministry spokesman said a fake fur version would have to satisfy "safety and durability considerations" and that "no alternative has met all those criteria to date".
The sharp increase in price is explained by the MoD as the result of a change in the "contractual arrangements" for the caps, which are all made from the fur of bears hunted in Canada.
The cost of the caps worn by the King's Guard rose from £1,560 each in 2022 to £2,040 in 2023.
Elisa Allen, of Peta, called on the MoD to "stop wasting taxpayer pounds on caps made from slaughtered wildlife, and switch to faux fur today".
The distinctive tall caps are worn on ceremonial events such as Trooping the Colour, and the figures from the MoD show that 24 new caps were bought in 2023 and 13 in 2022. Over the past decade the amount spent on replacement caps has been more than £1m.