A joint venture battery plant said on Thursday it will hike the wages of workers at its Ohio plant by an average of 25% after it came under harsh criticism from some senators for paying workers as little as $16 an hour.

Ultium Cells, a joint venture of General Motors and LG Energy Solution, said workers must still ratify the interim wage increase that takes effect Aug. 28.

Workers voted in December to join the United Auto Workers union but have not yet reached a contract.

The interim wage increase will be retroactive to December 2022 and some workers will receive between $3,000 to $7,000, based on hours worked, Ultium said.

(Reporting by David Shepardson; Editing by Chris Reese)