US President Donald Trump has signed into law a steep tariff on imported solar panels, a move billed as a way to protect American jobs but which the solar industry says will lead to thousands of layoffs and raise consumer prices.

China, the world’s biggest solar panel producer, complained the decision would undermine global trade.

The 30 per cent tariff on solar panels is among the first unilateral trade restrictions imposed by the administration as part of a broader protectionist agenda intended to help US businesses struggling to compete with companies producing lower-priced goods overseas.

The administration also introduced a tariff on imported washing machines.

“You’re going to have people getting jobs again and we’re going to make our own product again. It’s been a long time,” Trump said as he signed the order.

But the solar industry countered that the move will raise the cost of installing panels, quash billions of dollars of investment, and kill tens of thousands of jobs, raising questions about whether Trump’s move will backfire by triggering mass layoffs.

“We are not happy with this decision,” said Abigail Ross Hopper, president of the US Solar Energy Industries Association, on a conference call with reporters on Tuesday. “It’s just basic economics – if you raise the price of a product it’s going to decrease demand for that product.”

SEIA predicted that the tariffs could decrease the projected 11 gigawatt of solar forecasted to be installed in the United States this year by 2 GW and lead to the loss of 23,000 jobs this year.

The US solar industry employs more than 260,000 workers – about five times more than the coal industry. About 14 per cent of those 260,000 jobs are in manufacturing, with installers making up most of the rest of the industry.

Over the next five years, the tariffs are projected to reduce US solar installation growth by 10 to 15 per cent, research firm Wood Mackenzie reckons.

The petitioners who sought trade relief, US-based solar manufacturers Suniva and SolarWorld, had asked the Trump administration for the equivalent of a 50 per cent tariff, arguing they cannot compete with the cheap imports that have caused panel prices to fall more than 30 per cent since 2016.

The decision was a blow for overseas solar manufacturers, with industry experts anticipating fewer sales in the United States, the world’s fourth-largest solar market after China, Japan and Germany.

China branded the move an “overreaction” that would harm the global trade environment for affected products.

“The US’s decision … is an abuse of trade remedy measures, and China expresses strong dissatisfaction regarding this,” Wang Hejun, the head of the commerce ministry’s Trade Remedy and Investigation Bureau, said in a statement on its microblog.