THE LATE Yehudi Menuhin was among those who visited the Ashmolean Museum in Oxford to worship at the shrine of "the Messiah", one of the finest instruments created by the Italian master violin maker, Antonio Stradivari.

The Messiah is regarded as an exquisite example of Stradivari's work, an object of singular craftsmanship and beauty. It is also the best preserved of the 650 "Strads" that are still in existence. Now, though, in a move that has unsettled the genteel world of antique string instruments, doubts are being voiced about the authenticity of the violin, hitherto thought to date from 1716.

In the current issue of theJournal of the Violin Society of America, Stewart Pollens, the associate conservator of musical instruments at New York's Metropolitan Museum of Art, declares the Messiah to be a fake. He points to design features that distinguish it from other Strads, and scientific analysis that suggests it was made from a tree chopped down after Stradivari died.

Mr Pollens' findings have been greeted with dismay by, among others, the Hills family, who run a violin-dealing business and who donated the Messiah to the Ashmolean in 1939 after refusing a blank cheque for it from the American car magnate Henry Ford.

Andrew Hill, a senior member of the firm, this week dismissed the slur on the violin's reputation and described Mr Pollens as "a one-man vendetta, a person with an agenda, whose opinion I have no time for whatsoever".

Mr Pollens says that his doubts were triggered in 1997, when he first examined the Messiah and noted features inconsistent with the rest of Stradivari's work, such as the design of the f-holes, the curling apertures on the surface of the instrument.

He then asked Peter Klein, a dendrochronologist at the University of Hamburg, to date it. Dr Klein studied the growth rings in the wood and gave a likely date of 1738, the year after Stradivari died. Undeterred, the Hills family commissioned their own dendrochronologist, John Topham. His findings, according to Mr Hill, "confirm what we thought all along".

Dr Klein now calls his own findings "preliminary", saying that they were based on studying a photograph. Mr Pollens, though, is sticking to his guns.

In the middle of the argument is the Ashmolean. Timothy Wilson, the museum's keeper of Western art, said that questions had been raised about the Messiah in the past.

"Those who have maintained its authenticity have been a great deal more convincing than its occasional detractors," he said.