Facebook blocks Vintage Camera app
The developers of an application called Vintage Camera say Facebook has unjustly banned users from uploading their photos to the social network.
The app, which works on Apple devices, provides various effects to make pictures look dated.
French studio Presselite, which developed the app, says it has more than eight million users worldwide.
Facebook told the developers the decision had been made following negative feedback from account holders.
After Presselight appealed against the ban, Facebook sent the company an email saying: "We've checked out the circumstances of your app's restriction, and we found that your app received strong negative feedback from users and their friends.
"Unfortunately, we will not be able to restore your app's functionality."
But Presselite co-founder Antoine Morcos said that, according to administration data provided by Facebook itself, there had been about one negative report per 1,000 images shared via the app, which he believed had been due to "inappropriate use".
"We don't understand how Facebook could block the access to millions of users of the Vintage Camera application who want to share their photos on Facebook, only because of a few negative feedback reports," Mr Morcos wrote in a press statement.
"As you all know, Facebook has acquired the Instagram photo-sharing application, and we hope this acquisition is not influencing this kind of access limitation for other photo applications."
After being contacted by the BBC, Facebook said that Presselite had received warnings about the app before it was blocked.
"While we provide an open platform, every application on Platform is required to meet our policies. We take both automated and manual steps to detect violations and ensure compliance," the firm said.
"Pending on the violation, we give developers an opportunity to come into compliance via a warning system. In the case of this application, the application was not in compliance with our platform policies and had received three warnings prior to our systems taking action on the application."
The app has a four-star average rating on the Apple store, although some users have written in reviews it does not always work and others complain it is too similar to Instagram,
In 2010, Presselite accused London-based developer Q Mapps of infringing its copyright, after both firms released an app called Paris Metro for Apple devices.
Presselite asked Apple to remove the Q Mapps app from its store but was found to have had its trademark application rejected by the US Patent and Trademark Office.
At the time, developer Malcolm Barclay described the allegations as "utterly baseless and false".