Makino Milling Machine Co.’s official labor union has reiterated its opposition to Nidec Corp.’s $1.6 billion offer to acquire the machine tool maker, arguing that the business sense of any deal remains unclear.

In a news conference, union members stated their continued resistance to a takeover by Kyoto-based Nidec. They expressed concerns over the unsolicited bid initiated in December, citing Nidec’s past acquisitions that resulted in deteriorating working conditions at target companies. This stance was supported by more than 90% of the union’s 952 members in a letter addressed to Makino Milling President Shotaro Miyazaki in January.

Unsolicited bids are uncommon in Japan, where strong labor laws often prevent widespread layoffs and require consensus building with target companies. Since receiving Nidec’s offer—which has a market capitalization more than 10 times its size—Makino Milling has reported receiving several early-stage buyout proposals. The company has requested a delay in the start of Nidec’s proposed tender offer from April to May to allow time to compare the different proposals.

Makino Milling is currently fielding approaches from MBK Partners and Nippon Sangyo Suishin Kiko Ltd., raising the possibility of a takeover battle.