Several children's books have been recalled from schools after some copies included a web address that led to a website featuring porn.
Andrew Cope's popular series, The Spy Dog, features in schools and libraries across Britain.
But, some of the books which were published by Puffin and aimed at children between seven and 12 were found to include a web address leading to a page which featured pornographic content.
It is believed some of the content features pornographic animations of well-known Disney characters.
Puffin, which is part of the publishing giant Penguin Random House, issued the urgent recall of the books.
It announced that all sales of the affected books had been "immediately paused".
Schools and local councils across Britain have warned parents about the link and urged them to check their own copies to make sure they did not include the inappropriate link.
The web address had once led to Cope's official site, however, the domain name was "taken over" by a third party which hosted "inappropriate adult content".
Andrew Cope released a statement with Puffin, saying an unconnected third party had taken control of the domain name
|What is understood to be the offensive website, contains adult pornographic videos.
A number of these feature titles and descriptions are written in Arabic.
The website also features Japanese animated pornography, AI-generated videos and subsections for "adult dating" as well as "gay dating" and "games".
One of the schools which issued a warning about the "safeguarding risk" accidentally included the website link in an email - which directed parents to the porn site.
Author Andrew Cope with the books in 2009
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Hordle C of E Primary School in Hampshire sent a second email two hours later.
"Further to the email sent out earlier today, we are sorry to report that the details of the safeguarding concern regarding Spy Dog have created an automatic web link to the site mentioned," it said.
"Please DO NOT click on the link and delete the original email received.
"Please accept our sincere apologies for the issue."
One parent "burst out laughing" when he realised his child's school had sent the link.
The father said he thought it was funny.
"How kind that the Church of England not only cares about our spiritual health, but also our sexual health," he said.
Mr Cope and Puffin said in a joint statement: “In some editions of the Spy Dog, Spy Cat and Spy Pups series there is a reference to the author, Andrew Cope’s, former website for the series, which was owned and managed by him."
“We understand an unconnected third party has very recently taken control of the domain name and is using it to display a different website with inappropriate adult content," the statement further read.
“This website is not associated with Puffin or Andrew Cope. We are asking people not to visit the website and ensure that children do not visit it either.
“We are taking this extremely seriously and are acting on this issue as a matter of urgency through the appropriate channels to get this website removed.”
Penguin immediately blocked sales and issued recalls on the books, removing the section of its own websites, advertising the series.
The site has since been shut down by UK registry of web domains, Nominent.