Companies in the sector offered a wage increase of 1.2 percent, which IG Metall said comprised a one-time payment of 0.3 percent and another 0.9 percent over 12 months.

That was well below IG Metall's demand for wage increases of 5 percent for 3.8 million metals and electrics sector workers after the German economy grew by 1.7 percent last year.

"This is not an offer, this is a provocation for all of IG Metall," Knut Giesler, the union's regional leader for NRW, said.

(Reporting by Matthias Inverardi; Writing by Maria Sheahan; Editing by Michelle Martin)