More than 500 jobs are at risk at an aluminium plant after the company failed to secure a deal for a new electricity supply.

Anglesey Aluminium Metal (AAM), one of the area's biggest employers, is to end smelting in Holyhead in September.

The company relies on power from the nearby Wylfa nuclear station, which is due to close next year. It denied its decision was due to a market downturn.

Politicians have warned of a "dreadful" social and economic cost if it closes.

Anglesey Aluminium uses 12% of all the electricity supplied to Wales, and is believed to be the biggest single user of electricity in Britain.

But with the planned closure of Wylfa's nuclear plant in 2010, AAM has been forced to examine other power supply options.