SCOTLAND is losing out on a number of important works of art as the national galleries struggle to compete in the international market, experts have warned.

James Holloway, the director of the Scottish National Portrait Gallery, said a number of “key Scots” were missing from the portrait collection and admitted he did not have the budget to buy an important portrait of Robert Louis Stevenson that is to be auctioned next week.

The painting of Stevenson and his wife – which the author once described as excellent but “damn queer” – is expected to fetch up to £3.9 million when it goes on sale at Sotheby’s in New York.

Dating from 1885, John Singer Sargent’s painting is described in the catalogue as “the best known and most widely recognised of the striking, informal portraits John Singer Sargent began painting in the early 1880s”.

Mr Holloway told The Scotsman: “I would love to have it. It is such a good picture and tells you so much about Robert Louis Stevenson. It is also a commentary on his American years, which is something we do not do in the gallery. I would be sorry not to have it but our acquisition budget for this year is extremely limited.”

Last year, the National Gallery of Scotland bought Titian’s 500-year-old masterpiece Venus Anadyomene for £11.6 million with assistance from a one-off Executive grant and lottery money. However, the National Galleries of Scotland now has an annual budget of £1.2 million, but a large proportion of this is eaten up with running costs.

Mr Holloway added: “No curator is satisfied with his budget: we always want more. If we had more, we could do so much more.”

Less than two weeks ago, the Scottish National Portrait gallery missed out on the famed Albion Collection of portrait miniatures which sold for more than £1.5 million in a sale at the art auctioneers Bonhams.

The National Portrait Gallery opened its doors in the late 19th century and boasts a “unique visual history of Scotland”. Among the most famous portraits are those of Mary, Queen of Scots, who stands in brooding isolation, Allan Ramsay’s portrait of the philosopher David Hume, Alexander Nasmyth’s portrait of Robert Burns, and Sir Henry Raeburn’s Sir Walter Scott. But Mr Holloway admitted that there were a number of eminent Scots missing in the collection.

He said: “There are a number of key Scots who we do not have in the collection who we would like to have.

“One of the people who I really feel is a major omission is James Clerk Maxwell, who is perhaps the greatest scientist, certainly between Newton and Einstein. Not to have him is a disappointment.

“Closer to date, we do not have Edwin Morgan, who we don’t really represent properly.

“There are also areas that we are not very good on, such as sport. Sports people are always difficult to get because they peak quite early. They tend to get painted when they have hung up their boots.”

The warning that Scotland is missing out on art treasures comes just days after it was revealed that the country spends less than half of 1 per cent of its public funding on the arts. A report by the Cultural Centre for Policy Research at Glasgow University showed that the Scottish Arts Council’s core funding for arts organisations has experienced only a marginal increase.

David Patterson, the deputy keeper of fine art at Edinburgh’s City Art Centre, said the Stevenson portrait would ideally come to Scotland – but ruled out a bid from his gallery.

“It is a very special painting. It has an unusual composition and it seems to capture Stevenson’s fragility. It would be fantastic if someone had the wherewithal to buy it for the nation,” he said. “The City Art Centre has a bequest fund which was left in the early 60s, but the actual money varies from year to year as we take the interest from it, and what we have left depends on what we have purchased the previous year. But we are talking in the region of £30,000 to £40,000 a year.”

Stevenson was born in Edinburgh’s New Town in 1850. He died 44 years later on a small Samoan island in the Pacific. During his short life, he travelled the world, defied convention, and made himself one of the most famous writers of the 19th century.

Dr John Scally, the director of collections at Edinburgh University and author of Pictures of the Mind, the illustrated Robert Louis Stevenson, described him as one of Scotland’s great lost geniuses.

“Stevenson, in terms of the animation of the memory of Scottish people, is stronger than any other author because of the nature of the books that he wrote. He is an author that caught people in their childhood and that is carried into adulthood. When he died, in his early 40s, he was just coming into his best period as a writer, so we will never know how good he was.”

Despite Stevenson’s Scottish roots, many of his literary manuscripts and artefacts have ended up on the other side of the Atlantic.

Dr Scally added: “It is a consequence of the much-travelled Stevenson that most of his estate is outside of Scotland. Stevenson died in Samoa, his wife was American and most of his artefacts and literary manuscripts ended up in America through a number of private sales in New York.”

A spokesman for the Scottish Executive said: “We would welcome a buyer from Scotland but it is an open auction. The National Galleries of Scotland has acquired fairly significant works of art in the last three years and we have certainly assisted them in doing that. They have a budget and have to balance their priorities.”