Authors are mourning the closure of Authonomy, the online community for would-be writers set up by HarperCollins seven years ago as a way to source new talent.

Described as an “open slush pile” by Cory Doctorow when it launched in 2008, Authonomy allowed users to submit their manuscripts for discussion, critique and ranking by fellow site members. The top five each month were read by HarperCollins editors, with 47 going on to be picked up for publication, including works by Miranda Dickinson, Steven Dunne and Kat French.

But HarperCollins announced on Wednesday that Authonomy would close at the end of September, telling writers that “in recent years publishing of titles from the site has slowed as we have opened other submissions channels, and the community has become smaller, so the decision to close Authonomy has been made”.

Dickinson, the bestselling author of titles including Fairytale of New York, wrote on Twitter: “Really sad to hear @authonomy is closing. I have a career today because of that site.”

Really sad to hear @authonomy is closing. I have a career today because of that site. http://t.co/1MMNlhATdn — Miranda Dickinson (@wurdsmyth) August 19, 2015

“This is very sad news indeed. I’ve been extremely fortunate to have had this relationship with Authonomy. The site was invaluable to me when I started reaching out with my writing; the connections I’ve made over the past five years have made all the difference. I owe everything, career-wise, to that initial decision to post my work,” wrote Mary Vensel White, whose thriller The Qualities of Wood is published by HarperCollins, in response to the announcement.

Liz Tipping, whose novel Five Go Glamping is due out from HarperCollins, also regretted the news. “My novel Five Go Glamping started life on Authonomy too. I uploaded it on Authonomy when it was just a few thousand words long and had requests from editors to see it – that encouraged me to keep me writing. It’s being published next Friday by the HarperCollins imprint, Carina,” she wrote.

There are around 150,000 people signed up to Authonomy, said HarperCollins, stressing that they were not all active users. Scott Pack, who ran the site before he left HarperCollins last year, described it as an “absolutely fantastic idea, well executed and set up brilliantly”, but said that after a while “people learned how to game the system”.

“The idea was that the most popular books rated by members of the site would go to the top and would be read and reviewed by HarperCollins editors. For the first year or two, the top five were usually really good books, and the strike rate of finding things to publish was pretty high,” said Pack. But then “the focus of the vast majority of members was how to get into the top five, rather than how to make their work as appealing to HarperCollins as possible”, he said, with members trading positive reviews with each other to crack the top five, rather than rating work on its own strengths. “And the problem was, the strike rate was dropping off”.

Pack added that when Authonomy was launched, there was no real opportunity for a writer to prove their work was good, if they couldn’t get an agent or make it out of the slush pile. But now, with options such as Amazon’s Kindle Direct Publishing, a writer “can publish their work themselves, and sell 10,000 copies, and might not even want a publisher”.

HarperCollins chief executive Charlie Redmayne said in a statement that Authonomy “enabled us to meet and discover some amazing authors”, but that “now in 2015, and thanks to the pioneering work of the Authonomy community and team, our commitment to the discovery of new writing talent runs through our entire business and is reflected in our dynamic, genre-focused, digital-first lists such as HarperImpulse, and our open submissions windows for innovative commercial imprints such as Voyager and The Borough Press.

“We hope that the very talented Authonomy members – and all budding writers – will take advantage of these opportunities to continue showing us their work,” said Redmayne.