Unions are seeking urgent talks with the Government and Vauxhall after describing plans to cut 400 jobs at the car giant as a "major blow".
The jobs will go at the firm's Ellesmere Port factory by the end of the year after the company said it is facing "challenging European market conditions and a declining passenger car market".
Unite said it was seeking meetings with the Government and Vauxhall's parent company PSA to discuss future investment and ensure there were no compulsory redundancies.
General secretary Len McCluskey said: "To lose 400 skilled jobs, albeit on a voluntary basis, is a major blow to the automotive industry and its supply chain. It is also another huge loss for the north west economy.
"Quite clearly, economic concerns are having a serious impact on consumer confidence. When people feel insecure about the future they do not invest in expenditure like a new car.
"Our priority now is to support our members and protect this plant. We are calling for meetings with the highest levels of the parent company PSA to ensure that there are no compulsory redundancies and that our plant continues to attract much needed investment. That includes removing the uncertainty about a new model and clarity on Ellesmere Port's future.
"But we also appeal to the government for its assistance. This industry urgently needs economic and trading certainty so that it can build for a strong future in the UK.
"We ask that ministers give PSA and other manufacturers a clear signal that government will do all it needs to do to support this crucial sector through the Brexit process."
Rebecca Long-Bailey, shadow business secretary, said: "After the Government pledged to do everything it could to protect Vauxhall workers when PSA took over the company earlier this year, we are now seeing potential job losses.
"The Government's lack of a bold and consistent industrial strategy is holding Britain back. The Government cannot simply offer secretive bespoke deals to some car manufacturers and not others.
"The Government urgently needs to support the plant, provide Brexit certainty to the sector and attract the investment it urgently needs."
Vauxhall said in a statement: "Vauxhall needs to adjust production volumes at its Ellesmere Port production facility to the current level of demand, to improve its performance and protect its future as the industry faces challenging European market conditions and a declining passenger car market.
"As an important element in accelerating the recovery of plant productivity, while continuously improving the already high level of quality achieved today, Vauxhall plans a move towards single shift operation at Ellesmere Port during 2018.
"Vauxhall will consult with employee representatives and will look for potential opportunities to minimise the impact of these proposed headcount reductions.
"PSA Group has affirmed its commitment to the Astra plant at Ellesmere Port. The company has every confidence in the capability and skills of the Ellesmere Port workforce to deliver the necessary improvements in financial performance.
"Once it has enough visibility on the future trading relationship with the EU, and the plant competitiveness has been addressed, the company will be in a position to consider future investments."