"The print dictionary market is just disappearing, it is falling away by tens of percent a year," said Nigel Portwood, the chief executive of OUP.

Sales of the third edition of the Oxford English Dictionary (OED) have fallen and will never appear in print again because of the impact of the internet on book sales, according to its publisher.

Now a team of 80 lexicographers has been working on the third edition of the OED3 for the past 21 years.

The dictionary's owner, Oxford University Press (OUP), said the impact of the internet means the third edition of the OED -- known as OED3 -- will probably appear only in electronic form.

It is still estimated to be more than a decade away from completion; only 28 percent has been finished to date.

Asked if he thought the third edition would be printed, he said: "I don't think so." Portwood said printed dictionaries had a shelf life of about another 30 years.

OUP said it would continue to print the more familiar Oxford Dictionary of English, the single-volume version sold in bookshops and which contains more contemporary entries such as vuvuzela, the plastic trumpet encountered in the 2010 football World Cup.

"Books are about to vanish; reading is about to expand as a pastime; these are inescapable realities,"said Portwood.

The most recent OED has existed online for more than a decade, where it receives two million hits a month from subscribers who pay an annual fee of 240 pounds.