A pair of Florida men have sued Apple for allegedly misrepresenting the amount of storage room available to owners of 16GB iPhones and iPads.

The two, Paul Orshan and Christopher Endara, accused Apple of "unfair, unlawful, and fraudulent business acts or practices," including false advertising, and asked a California federal judge to designate the lawsuit as a class action so that others can participate.

In the complaint filed Dec. 29, Orshan's and Endara's lawyers claimed Apple failed to tell buyers that a fifth of the 16GB in low-end iPhones and iPads is occupied by the operating system and pre-installed apps, leaving consumers less than the full amount for their own content, such as apps, photos and other files.

"Reasonable consumers do not expect this marked discrepancy between the advertised level of capacity and the available capacity of the devices, as the operating system and other storage space unavailable to consumers occupies an extraordinary percentage of their devices' limited storage capacity," the complaint stated.

By the plaintiffs' calculations, a 16GB iPhone 6 had 13GB of space available to the user, while the 16GB iPhone 6 Plus and 16GB iPad Air had 12.7GB and 12.6GB, respectively. The portions of the 16GB inaccessible to users ranged from 19% to 21%.

The lawsuit also charged Apple with a Machiavellian strategy that used the disparity between the advertised and actual user-available storage space to push customers into paying for iCloud premium plans. "Using these sharp business tactics, defendant gives less storage capacity than advertised, only to offer to sell that capacity in a desperate moment, e.g., when a consumer is trying to record or take photos at a child or grandchild's recital, basketball game or wedding," the lawyers wrote.

Apple charges $0.99 per month for an additional 20GB -- above the free allotment of 5GB -- with other plans ranging from $3.99 monthly (for 200GB) to $19.99 per month (for 1TB).

Although the complaint claimed that, "It does not appear that Apple permits users of its devices to access cloud storage from other vendors," that is not the case: iOS users can use the free storage or paid options of a variety of services, including Dropbox, Microsoft's OneDrive and Google Drive.

The putative class-action lawsuit was similar to one that targeted Microsoft in November 2012 over alleged misrepresentations of the user-available space on the Redmond, Wash. company's Surface tablets. The 64GB Surface Pro 3, for example, has approximately 37GB for user content, meaning that about 42% of the stated space is reserved for the operating system and other files.

A federal judge ordered the parties to enter arbitration in February 2013, the last action taken in that case, according to court records.

On its website, Apple explains how it calculates storage space on its iOS devices, but unlike Microsoft for its Surface, has not published figures for user content.

Lawyers for the iOS lawsuit's plaintiffs have not responded to questions.