(Reuters) - EU plans for a higher tax on fiberglass imports from China look set to pass into law next month despite concerns the tariffs will limit supply of the lightweight material, used in wind turbines, cars and ships.

A proposal by the European Commission, the European Union's executive, to impose an extra 43.6 percent tariff from September 16 won support from seven of the EU's 27 states in a vote on Thursday, with 12 opposed and 8 abstaining, EU diplomats told Reuters.

Under EU law, an abstention counts as a vote in favor of a proposal, resulting in a final tally of 15 for and 12 against.

The decision means import tariffs on Chinese fiberglass are now likely to rise from 7 percent to 50.6 percent.

The move follows complaints by European producers that Chinese exporters were dumping fiberglass on the market at illegally low prices, threatening jobs at producers such as PPG Industries and Saint-Gobain Vetrotex.

European fiberglass users are opposed to the higher tariffs, arguing that the duties will create supply shortages and raise production costs for thousands of companies involved in turning fiberglass into composites used in wind turbines, lightweight hulls for ships and in cars.

EU diplomats opposing the measures said earlier this week they expected Thursday's vote to block the tax.

Abstentions by the Czech Republic and Belgium -- tipping the vote in favor of duties -- were not expected and could now pave the way for duties to stay in place for up to five years, one diplomat said on Friday.

"It's harder to get rid of an EU measure once it's on the statute books," the diplomat told Reuters.

The Commission's plans are for temporary measures. These would take effect while an investigation into Chinese fiberglass exports continues. Definitive five-year duties must be approved by the 27-nation bloc and launched by March 2011.