Buckingham Palace should be open all year, with the money earned used to pay for its upkeep, an antimonarchy group said.
This weekend, the palace opened for its first paying customers of the season, who were, in turn, able to see Palace refurbishments paid for by taxpayers.
Republic chief executive Graham Smith said the group accepted the palace’s significance and importance, but a new way of paying for its repairs was needed.
“With that ticket revenue that you raise, you will then be able to fund these sorts of repairs and restorations without coming back to the Treasury,” he said.
“We have hospitals and schools, police services struggling to make ends meet.
“We have arguments about public sector pay being kept down and all the while, we are pouring millions and millions of pounds into fixing this one building. It is an absurd waste of money.”
Visitors this season can see the results of the refurbishment, paid for with the government-approved sovereign grant, and a platinum jubilee exhibition.
“Buckingham Palace should be open all year round, but it is now largely a ghost building. People don't live there,” Mr Smith said.
“The Queen is in Windsor, Charles lives in Clarence House or Highgrove or one of his other many homes, and it is largely just housing staff as far as I am aware.
“There just is no justification for leaving it standing there unused, all year round, except for the occasional garden party.”
Buckingham Palace was first opened to the public in 1993 after a fire devastated Windsor Castle, where the queen now lives.
There was a deal that money from palace visitors would fund the repairs at Windsor.
Politicians agreed in 2017 that the sovereign grant would be increased over 10 years to allocate £369m to refurbish Buckingham Palace.
The costs last year were £47.8m, £16.2m more than the year before.
Buckingham Palace enjoyed a starring role in the queen's jubilee celebrations that included an aerial fly-past and a concert.
Queen Elizabeth II also travelled up from Windsor for a balcony appearance.
Jubilee celebrations
