A record-breaking year for publishers has been greeted with renewed demands for authors to receive a bigger slice of income and investment, as sales of books passed the £5.7bn mark in 2017.

Book sales income was up 5% on the previous year, according to annual figures released by the Publishers Association. In sharp contrast, a recent survey of authors’ earnings revealed a 42% drop over the last decade, with the median annual income now below £10,500.

Powering the record year for the UK industry was a 31% rise in hardback book sales income, as well as a 25% increase of income from audiobooks and an 8% uplift from exports. Income from fiction and non-fiction also rose, by 3% and 4% respectively, which the Publishers Association’s chief executive, Stephen Lotinga, said proved that people’s love of books showed no sign of waning.

“Publishers are catering to modern consumers who are reading books in different formats across different platforms, but still showing a very significant attachment to the printed word, as we continue to see the resilience and popularity of print across publishing sectors,” he said.

The figures did not include publishers’ profits, although the latest results from the two biggest publishers in the UK – Penguin Random House and Hachette Group – suggest increases in sales have not been matched by higher profits.

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However, authors contrasted the figures with a long-term decline in pay and investment in writers, particularly those yet to have a breakout bestseller. The author of Girl With a Pearl Earring, Tracy Chevalier, said: “Authors have seen their earnings chipped away at while publishers thrive.

“Most writers cobble together a living from several sources: teaching, journalism, and odd jobs. Writing is just one shrinking source of income. Shrink it enough and people will stop writing altogether. It literally won’t be worth it.”

Chevalier, who is also the president of the Royal Literary Fund, which supports writers in financial difficulty, said that the charity had noted an increase in applications for hardship grants from younger writers. She said it reflected publishers’ hesitancy to take a risk and support an author for more than one or two books at a time.

“I think writers starting out are getting less support from publishers – not just financial, but a commitment to develop them and see them through several books to build up a readership and steady sales,” she said.

Facebook Twitter Pinterest Joanne Harris says authors are being sacrificed for ‘wish-upon-a-star celebrity publishing’ Photograph: Murdo Macleod/Guardian

Joanne Harris, the author of Chocolat, agreed: “I am concerned that publishers don’t seem to be able to see beyond the next big blockbuster book by a white, American male in his mid-60s.”

She criticised the funnelling of funds towards celebrity and social media stars, which often failed to translate into sales. “Brooklyn Beckham received a huge advance for a £50 coffee table book of photographs that did not sell,” she said. “Authors are being sacrificed for ‘wish-upon-a-star celebrity’ publishing.”

The writer and critic Philip Womack also attacked the investment in celebrity authors. “When David Walliams’s last book came out they sent him on a helicopter tour of Britain, which strikes me as very extravagant when they could have used that money to give more support for debut and established children’s authors,” he said.

Nicola Solomon, the chief executive of the Society of Authors, hailed the figures as “excellent news for authors and for wider society”. She said she was concerned that publishers were investing in a shrinking pool of established writers and celebrities.

As a result, authors on the verge of success may never reach it, she said, pointing to the children’s author Geraldine McCaughrean, who was dropped after disappointing sales but has since won the Carnegie medal. “Publishers are acquiring lots of authors, but not always really investing in what they acquire, especially when they haven’t paid a fortune to acquire them,” Solomon said.

Lotinga denied authors were getting a smaller slice of the publishing cake. “I do not think that incomes are going down,” he said. However, he admitted publishers were hard-pressed to resist demands from retailers, especially supermarkets and online booksellers, in return for promoting individual titles. “Clearly when you are operating in a world where very large retailers are able to dictate prices in a massive sector, it is hard to fight,” he said.

In part, the failure to match profits with turnover has been laid at the feet of retailers, particularly Amazon, which holds a near-monopoly of online bookselling. One author, who asked not to be named, accused Amazon of using its power to keep book prices artificially low, which had undermined authors’ incomes.

“It’s Amazon’s fault entirely that book prices have not increased in the last 20 years,” he said, and referred to his first bestseller. “It was sold at £25 20 years ago and my latest book is also to be sold at the same price, which, in real terms, is a drastic cut.” When the author asked his publisher why prices hadn’t changed, he was told it was to ensure support from the online bookselling giant.

A spokesman for Amazon denied it pressurised publishers, saying it had no control over how publisher profits were distributed. “We focus on driving value and readership for authors as a top priority,” he said, adding that authors writing for its Kindle Direct Publishing arm could receive up to 70% royalties.