The company said the ageing power station which has dominated the coastline for 40 years would shut at the end of March next year. It had previously been expected to continue operating until December 2015.
Many of the 100 workers at Cockenzie will be offered redeployment to Longannet power station in Fife, though some are expected to take voluntary severance.
ScottishPower was given the go-ahead last year to build a replacement gas-fired power station within the structure of the existing plant, a move opposed by East Lothian’s SNP/Lib Dem administration.
But the statement on the closure said only that the company was “continuing to evaluate options for the development of the site”.
East Lothian council leader Paul McLennan said he was seeking a meeting with Scottish- Power senior managers. He said: “Last year it seemed very clear what they were planning to do, but their statement now is not so clear. We need clarity from ScottishPower about their long-term intentions.”
The existing power station has been operating on borrowed time since 2008 when ScottishPower opted not to invest in bringing it up to new European standards.
As a result Cockenzie was allowed 20,000 hours of operation before closing. That was expected to mean shutting down in 2015, but with the plant used to generate extra power due to problems at Longannet and Hunterston, the closure date has arrived earlier than scheduled.
Neil Clitheroe, chief executive of ScottishPower Generation Holdings, said: “We will be working closely with employees at Cockenzie in the coming months and are hopeful alternative employment can be offered to all staff who wish to stay within the company.”
A statement from the firm added: “ScottishPower is continuing to evaluate options for the development of the site.”
Sources said the company was awaiting the outcome of a UK Government review of energy regulation before making a final decision on the new gas plant, which would employ around 50 or 60 workers. The result of the review is expected to be known later this year.
Isobelanne Robertson, who was in charge of a community council survey on the power station last year, said most people would be pleased to see the station go.
She said: “People told us they had had enough of the one that’s there now. They said it was noisy and dirty and they always believed when it went, it went. It was a bit of a shock when the proposal came out for the gas-fired one.”