The announcement came after Chancellor Gordon Brown and GM officials met union leaders in a meeting this morning.
GM also announced the plant's three shifts would be reduced to two.
The company said the move reflected the 'ongoing pressure' in the car industry to increase productivity and reduce costs.
Jonathan Browning, Vauxhall UK chairman, said: "We are seeking to achieve the job reductions through voluntary agreements with the employees affected."
Browning said the jobs were cut at Ellesmere Port because it was the highest costing plant in Europe. He said the actions taken today would ‘improve the competitiveness of the factory.
When asked if the plant was safe from closure, Browning said there was ‘still more work to do to secure the long term future’.
Derek Simpson, general secretary of Amicus, said the decision was 'another devastating blow to the car industry and UK manufacturing in general'.
It was previously predicted that 1,000 jobs would go at the site.
Amicus, a union representing workers at Ellesmere Port, said it would withdraw its £8 million fleet contract with Vauxhall if jobs went at the plant. It is currently in discussion with Japanese brands.
"Unless General Motors are prepared to treat decent men and women in Britain with some dignity we will cancel our £8m contract for Vauxhall cars.
"We will encourage our members to buy their cars from a manufacturer who supports the British economy and urge other unions to do the same.
"We will be meeting with Japanese manufacturers who employ UK workers and explore options for sourcing our car fleet from them," said Simpson, earlier this week.