One of the country's biggest unions has warned Vauxhall it will end its #8 million contract with the company and deal with one of its rivals if it makes significant job cuts at its main UK factory.
Amicus also threatened to encourage its one million members and their families, and members of other unions, not to buy cars from Vauxhall if redundancies are announced at the Ellesmere Port plant on Merseyside.
The warning inflamed the row over staffing levels at the factory amid union fears that up to 1,000 jobs could be axed as part of a production cutback.
Thousands of workers staged a lightning strike last Thursday which halted production of the Astra over fears that job losses were imminent.
Talks between union leaders and parent company General Motors will resume later today . Amicus general secretary Derek Simpson said: "Unless GM are prepared to treat decent men and women in Britain with some dignity we will cancel our #8 million 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."
Mr Simpson will meet MPs at the House of Commons tomorrow to present "incontrovertible proof" that labour laws were leading to the demise of the British car manufacturing industry.
The announcement of significant job losses at Peugeot, Ryton, TVR at Blackpool and now potentially Vauxhall was directly linked to the ease with which employers can sack UK workers compared to their other European counterparts, the union claimed.
GM Europe Chief Carl-Peter Forster has reportedly said that the idea of spreading cuts over the car giant's other European plants was "not super attractive."