App developer NimbleBit has published an open letter accusing social gaming giant Zynga of borrowing heavily from its hit Tiny Tower iPhone game when developing the Dream Heights game.

The letter said: “Dear Zynga, (all 2,789 of you!). We noticed you are about to launch a new iPhone games called Dream Heights! Congratulations. We wanted to thank all you guys for being such big fans of our iPhone game of the year Tiny Tower. Good luck with your game, we are looking forward to inspiring you with our future games! Sincerely, (all 3 of us), Nimblebit.”

Tiny Tower allows gamers to build their own skyscraper and manage the businesses and tenants within the building.

NimbleBit co-founder David March tweeted: “Even when you refuse to go work for Zynga, sometimes you end up doing work for Zynga anyway.” Suggesting Zynga had previously expressed an interest in the game fellow co-founder Ian Marsh added: “They did go the honest route and try to acquire us first.”

Zynga – which raised US$1 billion via an IPO in December – recently boosted its mobile capability by buying Germany-based Gamedoctors as well as US-based developers Page44, HipLogic and Astro Ape Studios.