"Without additional policies (the EU target) is not likely to be met," said the report, which was written by Dutch green energy institute Ecofys and has yet to be published.

All 15 EU countries have non-binding targets for increasing their share of renewables, but only four will reach them, the report said.

The study, carried out for the European Commission's energy department, predicted that wind and biomass would increase substantially, but not enough to fulfil the targets.

"There is not sufficient policy to support it," Kornelis Blok, Ecofis director and professor at Utrecht University told Reuters.

"Feed in" policies, which guarantee premium prices for power generators putting electricity on the grid and tax breaks were the most effective policies that would ensure rapid take-up of renewables, Blok said.

Countries with these types of policy were set to meet their targets, the report said. Spain, Denmark, the Netherlands and Luxembourg were on track. Germany, which has a strong feed-in law, would just miss its target.

All other EU countries would miss their targets, the report said.

Britain's aim to boost renewables to 10 percent from just two percent will fail, it said.

The study predicts that with current policies the share of green power will double to four percent.