David W Packard, whose family helped to found the Hewlett-Packard computer company, is concerned that the site may be poorly conserved or that excavation of the library may not continue unless he underwrites the work.

Herculaneum, south of present-day Naples, was buried by the same eruption that destroyed nearby Pompeii.

“It is hard to imagine anything more exciting than excavating at Herculaneum,” said Packard, who is channelling the money through a family institute. “We have spent around $2m (£1.1m) so far, much of it on conservation work. We have tried to work closely with the Italians, who have all the skills needed. But we can offer a degree of independence and financial security.”

There has been concern in academic circles that the already excavated parts of the Roman city are falling into disrepair and that there are no plans for excavating the Villa of the Papyri. The building, which contains the library, once belonged to Julius Caesar’s father-in-law.

The villa is regarded as one of the most important unexcavated sites in Italy. Previous exploratory digs unearthed 1,800 charred manuscripts, many of them unknown or known only through references in other works.

The scrolls were in crates and it appears that slaves were removing them from the libraries when they were inundated with ash from the eruption. Although they appeared to be in a poor state, scientists at Oxford University have been able to read them after subjecting them to imaging techniques.

It is believed that there are thousands more scrolls in the building, much of which lies beneath the modern town of Ercolano, and that they may include lost works by Aristotle, Livy and Sappho.

“Of course everyone wants to excavate the villa,” said Professor Andrew Wallace-Hadrill of the British School at Rome, which is managing work on the site. “The building itself is of major historic importance, but the priority is conservation.”

Packard, a former classics scholar who lives in California, runs the Packard Humanities Institute, which supports archeological work in Bosnia, Albania and other countries. Though the institute has an endowment of £375m, Packard is not making an open-ended pledge to support work at the site. But he added: “If the proper circumstances develop, we can afford to do it. It is not a problem of having to go out and raise the money. There are no catches.”

He said there should be no conflict between those who want to excavate the villa immediately and those who argue in favour of conserving the whole site, generally acknowledged to be in a poor state of repair. “It would be irresponsible treasure hunting to dig the choice parts of the site and then leave afterwards,” he said.

Professor Robert Fowler of the Herculaneum Society, formed last year to support work at the site, said: “The work now being done by Mr Packard at Herculaneum is admirable and important.”

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