A New York man is suing Apple over the Siri voice assistant feature on the iPhone 4S, saying that it doesn't work as advertised.

The Wall Street Journal reports that Frank M Fazio, who is being represented by the Robbins Geller law firm, alleges that Apple's iPhone 4S advertising gives a "misleading and deceptive message" about Siri’s capabilities.

Siri, Fazio says, is "at best, a work-in-progress", as it had either completely failed to understand his instructions or responded slowly and incorrectly when asked for directions or to locate a certain store.

iPhone 4S users in the UK will be familiar with this situation, as Siri can "only look for businesses in the United States, and when you're using US English". However, this has always been the case since the device launched - one of its key selling points in the US is that Siri can help you find locations.

As the lawsuit, filed in a federal court in California, attests: "In many of Apple’s television advertisements, individuals are shown using Siri to make appointments, find restaurants, and even learn the guitar chords to classic rock songs or how to tie a tie."

The full text of the complaint can be seen below.

Meanwhile, the Japanese language support brought to Siri by iOS 5.1 isn't working as well as hoped for some users, Kotaku reports.

In testing against Syabette Concier, a voice assistant service provided by network operator DoCoMo, Siri came a poor second.

"Aside from Siri's inabilities to interpret certain vague phrases or comprehend uncommon Japanese phrases, its loading time is far longer than the Syabette Concier. Not to mention how some reactions were very unnatural and rigid. It seems as though Siri is spread too thinly with so many languages to support at the same time," the report's author Toshitaka Tachibana wrote.

Earlier this week, Macworld reported that Tim Cook had responded to an Italian customer's email asking about Siri support for Italian with a promise that the feaure would be added before the year is out.