Spiralling UK energy costs have been blamed for the planned closure of Sunderland's last commercial glassware factory and the loss of 240 jobs.
ARC International, which makes the Pyrex and Luminarc brands, also blamed the high costs of UK raw materials.
The company said the plant, in the Pallion area of the city, lost £760,000 in 2006 alone.
A spokesman said talks with union officials had begun and the factory was due to close in September.
A company statement said: "This plant has not managed to overcome some economic difficulties.
"The cost of power supplies in the UK has doubled over the last four years and the cost of raw materials is much higher than on the European continent.
"The production capacity is not sufficiently exploited.
"This has meant structural losses over several years, with no sign of an upturn, in spite of the full commitment of the staff to the productivity efforts."
Francisco Azcona, general manager of ARC, added: "The decision is based solely on the continuing adverse situation in our plant and in no way reflects on the performance of the employees.
"We must now do everything we can to help them in this transition period. I would like once again to express my gratitude for all their efforts."
ARC took over the Pallion plant, which has been producing glass for more than 90 years, from American firm Newell Rubbermaid in 2005.
Last year US-based company Corning announced it was closing its Sunderland factory in March 2007, with the loss of 100 jobs.