When the new £20m Queen's Gallery at Buckingham Palace opened last week, it was hailed by many as another example of the monarch's willingness to increase public access to the crown's vast collection of treasures. According to the Royal Collection Trust, which through admission and retail revenues is responsible for the collection's presentation and maintenance, the much improved gallery will now offer visitors the chance to see an annual rotation of about 450 of the "best" pieces, including Old Master drawings, Fabergé eggs and rare Baroque furniture.

But this apparent generosity only extends at any one time, even by the Trust's own admission, to 0.1% of the collection. Tot up what can be seen by the public at the other royal palaces and on exhibition "by gracious permission of the Queen" and her subjects are only ever able to view a tiny fraction of one of the world's most impressive art collections - one that is commonly but incorrectly said to "belong to the nation".

As with most crown assets, the ownership status of the Royal Collection and the crown jewels has been muddied by time and different people's interpretations. According to the Royal Collection Trust's latest annual report, the collection is "held by the Queen in right of the crown". The Treasury's long-held viewpoint is that the crown jewels, for example, are "non-surrendered crown property" which are "vested in the sovereign and cannot be alienated." However, the Duke of Edinburgh, in a TV interview in 2000 speaking about the Royal Collection's masterpieces, said that the Queen is, "technically, perfectly at liberty to sell them" - a viewpoint seemingly at odds with the "inalienable", namely non-transferable, status of the collection preferred by others.

The confusion is compounded by a statement by the then Lord Chamberlain, Lord Cobbold, to a select committee in 1971 in which he said that the Royal Collection is made up of items "purchased or acquired by all sovereigns up to the death of Queen Victoria". This seems to imply that jewellery and art bought by or gifted to monarchs since 1901 are part of their private wealth.

There would, however, be no room for confusion, argue republicans, if the collection of treasures was officially state-owned and its trustees were answerable to parliament as is the case with the collection held by, say, the British Museum. Following the Windsor Castle fire, for example, we, as subjects, had no way of knowing how or even if the Royal Collection is insured ("We never discuss such matters," is the official if curt response from the Trust), whereas our elected government could demand such information from the British Museum's trustees.

The government also has a final say over the fate of British Museum items with controversial provenance such as the Parthenon Marbles. It couldn't, however, officially decide the fate of similarly controversial crown assets, such as the Koh-i-Noor diamond.

The status quo of the collection's ownership may not seem significant if it amounted to a handful of paintings and some jewels, but the crown holds arguably one of the world's greatest collections of treasures. Traditionally valued as "priceless", the few who have tried to make a market valuation have, in the past year alone, estimated that it is worth between £10bn and £12.7bn - and that's without taking into account the royal provenance of the collection, which would surely multiply its true worth many times over.

The collection's 600 drawings by Leonardo da Vinci alone are valued at £3.22bn. The crown jewels, traditionally deemed part of the Royal Collection, are also said to be priceless. Counted for the first time in 1998 for a crown-sanctioned book (that retailed at £1,000), the jewels amounted to tens of thousands of stones, including 6,000 diamonds in one crown alone. The largest, the 530-carat First Star of Africa, is the one in the head of the sovereign's sceptre and was valued in the early 1990s by the then Tower of London's deputy governor at approximately £80m.

But while the crown jewels have now been publicly counted, there still remains confusion about the total size of the Royal Collection. The Trust says it amounts to, "up to and including even the cups and saucers", roughly 500,000 items. Other experts who have gained extended access to the collection have recently estimated that the true number to be anywhere between one and two million.

In its defence, the Trust says it has been working since it was formed in 1993 to produce a list of the collection's items which is finally to be made public "later this year". Only then will a more detailed valuation be possible of a collection of treasures that most certainly does not belong to the nation.