In its Medium-Term Renewable Energy Market Report, the agency said that the growth in wind capacity is expected to slow over the next five years unless policy uncertainty is removed.
The IEA now expects installed wind capacity to be 536GW by 2018, 4% lower than it had predicted in its 2013 report.
"For wind, onshore and offshore, the forecast has been revised down in China, OECD Europe, the United States and Australia," the report said.
While it forecast a 14% growth in capacity for 2014, this is expected to have fallen to 9% by 2018. As a result, renewable installations may "fall short of the absolute generation levels needed to meet global climate change objectives".
Offshore wind is expected to be the hardest hit, with only 20GW predicted for 2018, down from the previous prediction of 28MW. The report found that the cost of offshore wind is not falling fast enough to bring about the level of development that had previously been expected.
Policy issues highlighted include non-economic barriersfor example in China, such as an absence of necessary grid integration, as well as the cost and availability of financing. In the European Union uncertainties remain over the nature of post-2020 renewable policy and the build-out of a European grid to facilitate the integration of variable renewables, it said.
Last year, global onshore wind additions of 34GW were the lowest since 2008, "largely due to a drop in new capacity in the US stemming from policy uncertainty over the renewal of federal tax incentives" at the end of 2012, the report found.
Worldwide investment in new renewable power capacity in 2013 was estimated at around $250 billion, down slightly on 2012 and lower than the $280 billion registered in 2011.