The International Energy Agency (IEA) is calling governments to adopt effective policies on renewable energy.

It believes key design principles could help to accelerate the exploitation of the large potential of wind, wave and solar power.

According to the IEA, nearly 50% of global electricity supplies will need to come from renewable energy sources if carbon dioxide emissions are to be halved by 2050.

Nobuo Tanaka, executive director of the IEA, says only a limited number of countries have implemented effective support policies for renewables.

"Much more can and should be done at the global level ... to address the urgent need of transforming our unsustainable energy present into a clean and secure energy future," he adds.

The IEA has launched a study entitled Deploying Renewables: Principles for Effective Policies, which analyses the performance of the renewables promotion policies around the world.

It recommends that policy design should reflect five key principles, including the removal of administrative hurdles and the development of incentives.

This week Friends of the Earth stated that the generation of renewable energy from wave power is a huge resource waiting to be exploited.