As many as a quarter of the top 100 Kindle books on Amazon.com are from indie publishers, according to data revealed at a trade presentation by the retailer.

A chart detailing the 25 top-selling indie titles in 2012 was passed on by an audience member via Twitter. Though the term indie is broad, covering everything from self-published authors to publishing houses that fall outside the big six, the news has been interpreted as a victory for the go-it-alone author. However in the US the term has come to mean self-published. A spokeswoman for Amazon.com said: "This figure is referring to Kindle books on Amazon.com in 2012, with 'indie' meaning books self-published via Kindle Direct Publishing (KDP). So a quarter of the top 100 bestselling Kindle books on Amazon.com in 2012 were self-published via KDP."

Writer.ly , an online marketplace that connects authors with freelance editors, book designers and marketeers, tweeted a picture of the chart on Wednesday. It displayed the top 100 books, with about a quarter of the covers highlighted, under the title "A Quarter of top 100 on Amazon.com Indie-Published".

The figure refers to Amazon's US book market but is a strong indicator of what's ahead for the UK. "If the UK isn't quite there yet then it's just a time lag – we are seeing that more and more of the top books around the world are published by authors themselves," said Orna Ross, director of the UK Alliance of Independent Authors, which represents self-published writers.

"We are in the middle of a major change. I wouldn't be at all surprised if we reached a situation where the majority of the top books are author-published. I don't see what would stop that," Ross said.

Writer.ly (@WriterlyTweets) A quarter of the top 100 books on Amazon are indie-published. pic.twitter.com/YDYTLLJLJZ

Hugh Howey, whose novel Wool became a self-publishing phenomenon after it was picked up by a publisher and hit the US bestseller lists, tweeted: "Taken together, indie authors form a new major publisher to round out the big six." That's the level of sales we represent."On Amazon.co.uk, self-published works regularly show up in the top 100 bestselling books list, which this month includes The Girl Who Never Came Back by Amy Cross, a 30-year-old self-published writer of paranormal and fantasy, dystopia and erotica; and The One You Love by Paul Pilkington, the first in his Emma Holden suspense mystery trilogy.

Pilkington, a British university lecturer, said that sales "just took off" in July 2011, and he went on to sell more than 150,000 copies of two self-published novels after making the first book available for free as a taster. He hit the top of the Amazon Kindle chart first in the US, and two weeks later in the UK, and literary agents soon began circling. In the spring of this year he signed a deal with UK publishing house Hodder & Stoughton, which will publish his series in paperback in the UK and around the world in 2014.

"When I decided to self-publish it wasn't a means to an end – I didn't think I'd get a publishing deal," said Pilkington, who will continue working full-time as a lecturer. "I have a view that publishing is very fragile," he said.

Self-published authors who get picked up by traditional publishers are becoming a regular feature of the UK literary scene. Kerry Wilkinson was picked up by Pan Macmillan for his crime series starring detective sergeant Jessica Daniel, and the UK's bestselling self-published author of 2012, Nick Spalding, who sold 400,000 ebook copies of his romantic comedies, signed up with Hodder.

In November, 19-year-old physics student Beth Reeks was named as one of Time Magazine's 16 most influential teenagers in the world – alongside Justin Bieber and Barack Obama's daughter Malia – on the strength of her romantic fiction. Reeks, who began publishing while she was still at school in Newport, Gwent, publishes under the pen name of Beth Reekles, was scooped up by Random House after gathering a 19 million following with her first romance The Kissing Booth, which she published on the storysharing website Wattpad.

Richard Mollet, chief executive of the UK Publishers Association, which represents UK book publishing companies, said: "It is notable that very often those authors who find initial success from self-publishing subsequently work with publishers to take their writing career to the next level."

However, independent publisher Colin Robinson, of Or Books, sounded a note of caution about the figures, saying that a snapshot of all the books in Amazon.com's top 100 this week, as opposed to Kindle books alone, showed that "47 were from the big six publishers, 31 from other publishers I recognised, 21 from publishers I've never heard of, and one was definitely self-published"He added: "It's possible that some of the publishers I've never heard of are in fact imprints set up by the author of the book but, especially as several appeared with books by more than one author (or at least one author's name), it seems unlikely that more than a few are. Disney and Little Brown are doing great. So are joke books.".

Amazon has been careful not to ghettoise self-published works, instead listing them with equal ranking alongside those from traditional houses, in a move that has irked some established publishers and led to calls for self-published works to be categorised separately.Richard Mollet said he believed that "publishing companies still offer authors unparalleled creative, financial and marketing support and expertise, helping the author and the work achieve their full potential. Publishers offer to readers remains the discovery and delivery of the very best of creativity from the author community."

Amazon has rapidly built a leading position as a producer and distributor of indie works during the past few years, developing its ebook publishing service Kindle Direct Publishing, and CreateSpace, an online service for people who want to make their work available through on-demand print books, music CDs, and DVDs.

CreateSpace topped the league of self-published print book producers in the US, registering 131,460 ISBNs in 2012, an increase of 123% on the previous year, and of 3,300% compared to 2007, according to figures from US ISBN agency Bowker.