Public cloud services, which Gartner says are increasingly being adopted by enterprises, are both cannibalising and stimulating demand for external IT services spending, a survey by the analyst company has revealed.

Across June and July this year, Gartner surveyed 556 organisations from nine countries and industries where cloud planning is a critical issue, and found that adoption of public cloud services varies between each of the cloud deployment models.

Infrastructure-as-a-Service (IaaS), a cloud computing model that sees an organisation outsource the use of equipment, including storage, hardware, servers and networking components to a client, is moving from lower-risk pilot programs and into production environments, Gartner said.

Gartner said Software as a service (SaaS) adoption, particularly in large enterprise application suites, will continue to reduce the total potential market available for application outsourcing.

At the same time, Gartner said SaaS adoption in the short term will drive external IT services spending by offering consulting and implementation service opportunities for IT service providers, as well as ongoing integration and configuring.

The adoption of Platform-as-a-Service (PaaS), which allows organisations to create and deploy applications over the internet using hardware and software owned from public cloud providers, indicates the growing strategic importance for organisations to adopt cloud infrastructure to support their business needs, Gartner said.

Of the respondents, 19% are using cloud computing for most of production computing, the survey found, with 20% using storage as a service for all, or most, storage requirements.

Reduced spending is most noticeable in the data centre, Gartner said, where 14% of respondents plan to decrease external spending.

According to Gartner, 71% percent of leading cloud adopters expect to increase external spending on end-user computing infrastructure management, and 70% of leading adopters plan to increase external spending on application development.

However, in addition to cannibalising demand for outsourced services, Gartner said public cloud services are also stimulating the adoption of external IT spending due to service management responsibilities being moved externally from within the organisation.

"Public cloud adoption is accelerating and public cloud services do, and will, cannibalize IT services spending in the coming years, most notably in the data center," said Bryan Britz, research director at Gartner.

"At the same time, public cloud adoption offers service providers the opportunity to accelerate externalization of spending for the non-public cloud workloads and IT operations and service management responsibilities in tandem with clients pursuing a public cloud initiative," he said.