Fears that pirated editions of JK Rowling's upcoming novel The Casual Vacancy could leak out mean that some foreign publishers will not receive a copy of the manuscript until it is published in English, forcing them to rush their translations or miss out on sales.

Rowling's literary agency, the Blair Partnership, is withholding advance copies of the novel from its publishers in territories including Italy, Finland and Slovenia, because the territories are viewed as high risk for piracy and it wants to "minimise the risk of the manuscript being leaked".

The Casual Vacancy will be published on 27 September in the UK and the US. Publishers in France and Germany are receiving early copies to enable them to release their translations, Une place à prendre and Ein plötzlicher Todesfall, simultaneously. "We have agreed to let publishers in some countries publish simultaneously with the English-language release, as some publishers are better able to handle the security demands of a simultaneous release," literary agent Zoe King told Publishers Weekly.

The decision means publishers who have yet to receive a copy of the novel will have to rush to translate the book once they are sent it on 27 September, which its Slovenian editor Andrej Ilc told PW would "forc[e] publishers around the world to break all the rules of good translating and editing". "We will most likely be forced to employ more than one translator and abnormally speed up the editorial and production process to publish in time for the Christmas season," said Ilc.

In Finland, the process is moving even faster. "The translator has to agree, sight unseen, to turn in the finished copy in three weeks, by October 18, in time for release for Christmas sales. That's 23 pages of polished final text every day for 21 days – without time to read the book beforehand!" blogged Jill Timbers, a translator of Finnish books into English. Timbers said that discussion was "swirling" among Finnish literary translators about quality of translation, and "preserving true Finnish language versus slipping inadvertently into anglicisms under such time pressure".

"Some translators argue that it's good [that] bestsellers are translated into Finnish, even if time pressure means the level of the Finnish isn't top-quality," she said. But "there's a derogatory nickname in Finnish for translations that 'straighten all the curves', convey the storyline but skim past finer bits and nuances. Perhaps that wouldn't so diminish Rowling's new book? Who can say, since no one's seen it."

The move could "easily result in subpar, rushed translations," agreed Chad Post, who publishes English translations of international books at the University of Rochester's Open Letter Books. "It seems totally insane and stupid," he told Publishers Weekly.

But Rowling's agent Neil Blair pointed out that none of the Harry Potter books were ever published simultaneously, and said that the agency's concern was "more to protect fans' enjoyment (ie safeguarding secrecy of plot etc as a first principle) rather than to avoid piracy (ie to prevent pre-publication leaks. And obviously that risk increases each time we add one more publisher to the schedule. Each of the publishers understand and appreciate that."

Blair said that English and German editions of the novel would be published on 27 September, and the French edition on the 28th, "and all the rest sometime later", probably starting with Chinese and Dutch versions of the book "once they have all taken the time to produce a first-class translation".

He insisted that "no one is placing any pressure on the publishers to rush anything". "As I say, Harry Potter never came out simultaneously anywhere, so we and JK Rowling are actually doing more in that regard for this release. It's great that there is such huge interest in her next work and if that came with no possibility of a pre-publication leak then obviously we would have loved to have improved on that further."

The Casual Vacancy is Rowling's first adult novel. It follows the shockwaves that hit the small English town of Pagford when councillor Barry Fairbrother dies, as locals fight to take his place "in an election fraught with passion, duplicity and unexpected revelations".