Buckingham Palace is in need of £3m over the next three years to repair crumbling walls.
The walls and roof of Buckingham Palace are in need of repair
The monarch's official London home since 1837 was cited as an example of the work needed to make some of the royal palaces safe.
Details of the repairs were revealed in the Queen's annual public accounts, which show the royals cost £37.3m last year - 0.3% less than in 2005-6.
Anti-monarchy group Republic said the real figure was £150m, not £37.3m.
'Cracked and loose'
The Department for Culture, Media and Sport has overall responsibility for the maintenance of occupied royal palaces but management and operating responsibility rests with the Royal Household.
Sir Alan Reid, Keeper of the Privy Purse, has said there is a "critical backlog of maintenance projects" affecting the royal buildings.
He has asked for the grant that pays for the upkeep of the buildings, which was £14.5m during the last financial year, to be increased by £1m a year.
A senior palace aide said the feeling was they were "unlikely to be successful".
At Buckingham Palace, one of the four walls inside the quadrangle facing the Mall is crumbling and cracking after being eroded by the elements.
The wall, made of Caen stone from France in 1847, has cracked and loose stonework and some carved features have dropped off.
The other three walls, made of Bath stone from the Cotswolds, are in better condition.
The Queen's accounts also reveal that the Royal Family spent £1.1m on hospitality and £2.2m on helicopters.
In all, £5.6m was spent on travel, including £2.2m for 514 hours of helicopter use.
The Prince of Wales and the Duchess of Cornwall took the single most expensive trip.
Their tour of the Gulf states in February taking in Kuwait, Qatar, the United Arab Emirates and Bahrain cost £345,710.
A total of £8.8m was spent on salaries for Royal staff and £1.1m on hospitality and catering, including garden parties.
The Prince of Wales and Duchess of Cornwall toured the Gulf states
Sir Alan said the cost of the Royal Family had fallen by 2.7% in real terms from last year and 7% in since 2001.
"The reduction in the amount of head of state expenditure reflects the continuous attention the Royal household pays to obtaining the best value for money in all areas of expenditure," Sir Alan said.
But Republic, the campaign for an elected head of state, said £37m was "fantasy".
Campaign manager Graham Smith said the Royal Family had not included security costs or tax breaks in their calculation.
"This blatant spin would put Alastair Campbell to shame," said Mr Smith.
He added: "It is absurd that the royals still manage to spend tens of thousands of pounds on individual journeys within the UK.
"A first class rail ticket or even a private car would be a tiny fraction of the cost to the taxpayer and a lot better for the environment."
The Queen is now said to be following his Prince Charles's example in trying to reduce the Royal Household's carbon emissions.
Sir Alan said carbon emissions on gas and electricity had been reduced by 1,000 tonnes or 12% during the year, through lower energy consumption and the introduction of a new combined heat and power plant at Windsor Castle.