Dictionaries, long considered a must-have resource material, are being shunned in favour of internet sites as the digital revolution threatens to swamp the British book industry.

In the past four years, sales of English-language usage guides and dictionaries have plummeted by 40%, while other reference books, including maps, atlases and encyclopedias, have also shown a significant decline, according to research by Book Marketing Limited. Some publishers have even predicted that dictionary sales could cease completely.

In response to the decline, Oxford English Dictionaries will launch enhanced online services this year. Oxford University Press executive Casper Grathwohl said: "People still want dictionary authority and material, they are just going to different sources for it.

"Once you establish a brand in print and that is your medium for hundreds of years, it is a challenge to transfer to online, so there is nostalgia, but no more than in the fact that books in general are being superseded by online resources."

Grathwohl questioned the quality of some online dictionary services, but said that Oxford would live up to its scholarly reputation. He added: "It doesn't come in a nice package to give someone as a gift at Christmas or for graduation, but it's probably a better tool for them when they go off to university."

Julie Bertagna, bestselling children's author and a "reading champion" for the Scottish Executive's children's reading scheme, Read Together, believes there would be a loss "in so many areas of life" were dictionaries to disappear.

"At the moment I think we have a wonderful balance of reference systems with paper dictionaries and internet access," said Bertagna. "It's important for children to learn all kinds of reference skills, like using a dictionary and a telephone directory. Internet source dictionaries are also important because of the speed at which we are acquiring new words.

"I love dictionaries. This sounds really sad, but if I am stuck when writing a book, then I flick through a dictionary, as they are full of inspiration, taking you off on really interesting trails and detours, which you can't have with an online dictionary. I would hate for a generation of children in the future never to have that feeling."

Belfast-born writer Bernard MacLaverty says he has always been fascinated by dictionaries and encyclopedias. He said: "I remember before I started to write, reading Roget's Thesaurus for pleasure, with 21 ways of saying the same thing: boils, pimples, acne. I would go through it and think it was great.

"I can't imagine a house without dictionaries, but the shortcut that I have is an online dictionary in my internet favourites and I can check it without getting the sleeves rolled up to dust the dictionary down."

Publishers, authors and booksellers will meet today at the Booksellers Association Conference to discuss the future of the book industry and the decline of the reference book. Top of the agenda will be the effect of digital technology, particularly on specialist bookshops, with the arrival of e-book technology from the US likely to have great impact. The sale of downloadable books, now available from several companies, including Sony, totalled $15 million in 2005, up from $9.6m the year before.

Francis Bennett, managing director of information publishers BookData, said that while booksellers such as Waterstone's and Borders were working on digital strategies, many outlets and publishers were unsure what they should do.

"I don't think the industry has come up with any major solutions," he said. "It's a bit like planting seeds, and what we have got in the field is a few things popping up, but nothing has actually grown."

Bennett has been appointed chairman of the Booksellers Association Digital Task Force, which will create a blueprint setting out practical steps for booksellers considering selling digital products.

He added: "Ultimately, it allows us to get content to more people in more ways. I think it's a profoundly important development which will change the book trade for many years to come."