App-testing company warns that developers have not properly planned for the changes to the iPhone's software cause by iOS 7

Despite the excitement surrounding the imminent upgrade to iOS 7 (Apple’s latest mobile operating system) analysts are warning users that the new software might kill their favourite apps.

(Click here to read our guide to the new features offered in iOS 7)

Developers have had access to the iOS 7 beta for more than a month now, which in theory has given them plenty of time to update their apps to work smoothly with Apple’s new code. However on mobile apps analyst is reporting that "90% of iOS apps tested for first time are having trouble.”

This is according to Matt Johnston of uTest, an American startup that crowdsources beta testing of mobile apps for the likes of Google and Amazon.

Speaking to Business Insider, Johnston warned that some developers had simply ignored Apple’s warning to upgrade their apps: "I just talked to one large retail player and one large travel player and asked about iOS 7 upgrade plans and they said they didn't think it will that big a deal.”

Johnston says that this partly because previous iOS updates were more incremental but the differences between iOS 6 and 7 are dramatic in terms of both visual design and underlying code.

“When we moved from iOS 4 to 5 to 6, we weren't seeing this kind of spike in both performance issues and UI rendering issues," he said, before advising people to hold off updating, at least for a couple of weeks.

Despite Johnston's warnings, many app makers are already showing off their updated wares, and not only to boast of their compatibility with iOS 7. It seems that when it comes to user interfaces, when Apple says jump developers ask 'how high?', with many programs sporting new, sleek looks that are curiously reminiscent of the design language of Apple's new OS.

Apps including location log-in service Foursquare and Yahoo-Answers-for-grown-ups Quora are among the bigger names to 'put a fresh coat of paint' on their services, meaning that iPhone owners downloading iOS 7 have more than just Apple's updates to look forward to.