Enterprise adoption of cloud computing is being held back because of the complexity of companies’ own in-house legacy systems.

In a survey, over half of CIOs and senior tech professionals quizzed said their own IT architecture was the main hurdle to cloud adoption, and this jumped to 70 percent for respondents in the public sector. More than a quarter of the CIOs surveyed stated their legacy systems were too expensive – or valuable – to abandon altogether.

“The primary challenge of rolling out enterprise clouds is chiefly down to the complex interdependency of the systems involved, rather than skills or geography,” the research said.

Three quarters of the tech chiefs surveyed were using some form of cloud service; only six percent said they would never move systems to the cloud. But cloud remains at a relatively early stage of adoption, and the survey suggested it is being used more a “tactical bolt-on” rather than as part of a broader technology strategy: two thirds of respondents said they are using three or fewer cloud platforms, and more than two thirds said they have only been using cloud applications for less than two years.

As well as the complexity of their own systems, security was a key concern, especially for the public sector. But support and expertise from cloud providers is another concern, with 46 percent of the CIOs citing customer support as a main reservation when thinking about cloud adoption.

Kate Hanaghan, research director at analyst house TechMarketView said CIOs should be very wary of providers that are not able to explain the link between their services and the business benefits, because moving to cloud services is not just about the technology.

“The migration from traditional delivery to a hybrid cloud set-up that is fully integrated with the legacy estate can be hugely complex, and getting it wrong is not an option,” she said in a statement.

The survey of 300 UK CIOs and senior IT professionals was commissioned by NTT Europe.