The owners of Anglesey Aluminium Metal (AAM) have announced production will not restart at their Holyhead plant.
The smelting works will be decommisioned and only the re-melting operation, which employs about 90 people, will remain at the site, according to the company.
Smelting ended last September, with 400 job losses, because the plant could not source cheap electricity.
Anglesey MP Albert Owen said the announcement was not a surprise.
AAM said that over the last 18 months the company had worked with Anglesey council and the Welsh Assembly Government to investigate the possibility of using their site infrastructure and land to try and create as many jobs as possible for the local community.
The company said it hoped that over time there would be at least as many employment opportunities created as there were when AAM was fully operational.
Part of this activity has been allowing the use of the AAM jetty for cruise ships to berth.
A separate biomass project - to build a power station - will continue at the site.
AAM said that project may be sold "as a private business opportunity".
Anglesey MP Albert Owen said :"If the company was serious about continuing to smelter at the plant it would have taken up the generous government offer in 2009 to help bridge the gap over a difficult economic period globally," he said.
Mr Owen added he had been working with the company, and other potential investors, to try to create as many jobs as possible on the site.
"The Anglesey Aluminium site has a good infrastructure and is in an excellent location and frankly the company needs to leave as strong a legacy as possible and future jobs are the best way of doing this," he said.
"It is now vital that we all work together to create a skills base to attract and create quality jobs," he added.
Conservative economic spokesman David Melding AM said: "This news is disappointing but a consequence of allowing the decision on whether to re-commission Wylfa to drift for so long".
Anglesey Aluminium was established as a joint venture between Rio Tinto and Kaiser Aluminium in 1971.
Smelting work came to an end because agreement could not be reached on a new deal for below-market priced electricity to run the operation, despite high-level discussions and an offer to help the company from the UK Government.
Previously the plant was supplied with cheaper electricity from the nearby Wylfa nuclear power station but that is to end production at the end of 2010 - although there is an application for production to be extended to 2012.