The cost of the monarchy to the taxpayer rose by nearly six per cent last year - more than double the rate of inflation - as the royal household bucked the trend for austerity and dramatically increased spending on the upkeep of its palaces.

The Queen’s official expenditure from the Sovereign Grant, the amount released from the public purse each year to finance the monarch, increased to £35.7m - a rise of £1.9m on the previous year.

The steep rise included a 45 per cent increase in the amount spent on the upkeep of royal residences, including Buckingham Palace and the Kensington Palace apartments of the Duke and Duchess of Cambridge.

Public spending on refurbishing the 20-room central London living quarters of the couple and Prince George has totalled £4.5m over the last two years but royal aides said the cost of internal furnishings, including a new kitchen, had been met “privately” by the duke and duchess.

The Independent understands this cost was in fact met from the income received by the Prince of Wales and his dependents from the Duchy of Cornwall, which critics claim is effectively public money.

Royal aides insisted the £36m cost of the monarchy for the last financial year was equivalent to 56p per person in the country and represented “value for money”.

But campaigners said the considerable net increase in spending showed the Royal Family was badly out of step with public opinion at a time when Government departments were slashing budgets by up to a third, and millions of Britons have yet to feel the benefits of any economic recovery.

Graham Smith, chief executive of Republic, said: “An increase of this magnitude when everybody is dealing with cuts is frankly beyond belief. I think many people will struggle to comprehend how spending of this nature can be justified. It appears very much that the royal household believes it can get away with spending what it wants.”

Royal aides said that the annual accounts, published today in a glossy brochure, showed that a “backlog” of restoration work on residences including Windsor Castle was finally being tackled.

MPs earlier this year accused advisers to the Queen, whose personal wealth is estimated at £330m, of failing to control royal finances, reducing a reserve fund from £35m in 2001 to £1m last year, while palaces were “crumbling”. Margaret Hodge, chairwoman of the the powerful Commons’ public accounts select committee, called on the household to “get a much firmer grip” on its programme of repair works.

It is estimated that the total bill to secure the buildings stands at £50m. Last year, spending on property maintenance rose by £4.2m to £13.3m, including 133 projects costing £3,500 or more.

A quarter of that sum went on the cost to “completely reservice” Apartment 1A at Kensington Palace, the Christopher Wren-designed living quarters which were last refurbished in 1963 and now accommodate the Cambridges.

Renovation work on Kensington Palace cost £3.4m last year (Getty)

The two-year project involved the removal of asbestos and the overcoming of problems such as no running water, but aides said the duke and duchess had met the cost of internal furnishings, including carpets, curtains and a new kitchen.

An aide said: “Some of the fit out we felt should be paid for privately. The Cambridges have been extremely sensitive to the fact that public funds were paying for a lot of this work.”

A source underlined that the resulting accommodation was “not opulent”, adding: “It is done to a very comfortable but ordinary level.”

The Independent understands that the money spent by the Cambridges came from the income received by the Prince of Wales from the Duchy of Cornwall, which in 2012-13 stood at £19.1m. The Duchy, a sprawling collection of property, farmland and investments sectioned off to finance the heir to the throne 700 years ago, is classified as privately owned but campaigners have long argued its serves a public purpose by sustaining the monarchy.

Other maintenance costs met from the Sovereign Grant included £800,000 to remove asbestos in the basement of Buckingham Palace and £900,000 to renew lead roofing the Royal Library at Windsor Castle, where staff reportedly use buckets to catch rain and protect art and antiquities.

A royal source said the ability to tackled the maintenance backlog had been partly achieved by economies elsewhere, including a two per cent drop in staff costs and a seven per cent fall in travel expenses.

Travel costs incurred by the Prince of Wales, who has recently begun to take over official duties previously undertaken by his mother, included a £434,000 visit to India with the Duchess of Cornwall, and a charter flight to attend the funeral of Nelson Mandela which cost £246,160.

Sir Alan Reid, keeper of the Privy Purse, said the latest figures meant public funding of the monarchy had fallen by eight per cent in the last two when maintenance costs were removed.