The European Parliament threw its weight behind a transatlantic trade agreement on Thursday when the Socialists unexpectedly voted in favor of negotiations with the United States.

Trade committee deputies voted 28 to thirteen to support recommendations made by their German chairman, Bernd Lange, that stave off a confrontation with the European Commission. The bloc’s executive body strongly supports the tentative Transatlantic Trade and Investment Partnership.

Lange’s Progressive Alliance of Socialists and Democrats, the second largest group in the European assembly after the conservatives, had been uneasy about supporting the trade talks, fearing that a dispute settlement clause in the proposed treaty could allow companies to weaken European labor and food safety regulations. Yet almost all the group’s members voted in favor — as did the European Conservatives and Reformists and the liberals, the third- and fourth largest groups, respectively. The Greens and far left voted against.

EUobserver reports that a compromise between the conservatives in the European People’s Party and the Socialists calls for a new way to settle disputes with investors where cases are heard by “publicly appointed, independent” judges.

It also suggests that a public international investment court would be the “most appropriate” means to handle investment disputes in the medium term.

Lange told reporters after the vote that the current model for settling disputes between foreign investors and states was “no longer being tolerated” by the parliament. New legal instruments would have to be found, he said, “moving away from private courts.”

Although common to trade treaties, the proposed dispute settlement clause has become a lightning rod for opponents of an agreement that would encompass half the world’s economy and a third of its trade.

The European Commission says the treaty would raise global economic output €300 billion over the next ten years.

The European Socialists’ U-turn puts the ball back in the American left’s court. President Barack Obama’s Democrats are divided about free trade, fearing job losses in low-skill industries. Earlier this month, they refused to give him the authority to negotiate a separate trade treaty with Pacific nations — only to cave in days later.

Most Republicans, who control Congress, support both the Atlantic and Pacific trade negotiations.