Almost half of the top 50 apps on iPad are unavailable or have not been optimized for competing devices that run Google’s Android operating system. That’s according to a new report from Canalys, which believes Google should be doing more to encourage top developers to build high-quality tablet apps for its platform.

The data from Canalys shows that 30% of the top 50 iPad apps weren’t available at all on Android-powered tablets, while another 18% were there but they were not optimized for larger displays — they were simply smartphone apps that were automatically scaled up to fit a tablet screen.

That means just 52% of top iPad apps were also available on Android tablets.

“Quite simply, building high-quality app experiences for Android tablets has not been among many developers’ top priorities to date,” said Tim Shepherd, Canalys Senior Analyst.

“That there are over 375,000 apps in the Apple App Store that are designed with iPad users in mind, versus just a fraction of this – in the low tens of thousands – available through Google Play, underscores this point.”

Canalys does expect this to change as Android-powered tablets become more popular, but it still believes that “Google needs to do more to encourage greater numbers of developers to invest in delivering high-quality Android tablet apps quickly.”

If it doesn’t, the search giant runs the risk of “disappointing consumers with weak app experiences in the short term.”

Of course, one of the issues with Android, which can sometimes drive developers away from the platform, is piracy. Google’s “open” approach means it’s too easy for users to download and install apps from other sources without paying for them.

Back in July, we wrote about a game called Gentlemen! that had attracted over 6,000 players on Android during its first few weeks on Google Play. That’s an impressive number of players, until you consider that only 50 actually paid for the game, while the rest downloaded it illegally.

As a result of this, many developers choose to avoid Android altogether, while other must find different ways of finding revenue — such as ads. Of the 52% of top iPad apps also available on Google Play, six were titles that were paid on iOS, but were free and ad-supported on Android.

Canalys analyst Daniel Matte points out that while these titles may be free, they “typically deliver a poorer and often more limited user experience, sometimes taking a considerable toll on device battery life and often subjecting users to unskippable [sic] videos or other unpopular intrusions.”

With Google seeing lots of demand for the new Nexus 7, and Android tablets now commanding a larger market share than the iPad, it’s never been more important for it to put more focus on tablet apps.

Canalys believes it can do this by increasing the revenue potential of Google Play, and by changing the Play Store to “ensure more rigorously managed, high-quality, optimized experiences are highlighted, to the benefit of consumers, and to reward those developers who invest the time and resources in building them with improved discoverability.”

• SourceCanalys