Unions representing workers at the UK's last train builder have met with ministers to urge a crucial contract be reconsidered.
Derby-based Bombardier has said it will shed 1,400 staff after missing out on the £1.4bn Thameslink contract.
Unite and the RMT said they underlined to Transport Secretary Philip Hammond the impact on the area and the wider UK manufacturing industry.
The government has already said it is legally bound to uphold the decision.
Last month, the government awarded the contract to build new carriages for the rail route, between Bedford and Brighton, to German giant Siemens.
At the beginning of July, Bombardier announced plans to cut 446 permanent jobs and 983 temporary contract staff.
After the two-hour meeting, Unite assistant general secretary Diana Holland said: "He [Philip Hammond] has said, that at this stage, there is nothing further he can do.
"But he also said this process has not ended and the contract won't be signed for another few months. We are going to use that time to follow up on a number of issues."
Bob Crow, general secretary of the RMT, added: "The message to the people of Derby is that we're not going to disappear until the government can see what the social implications are for the people of Derby and beyond."
Mr Crow presented the minister with a dossier on the history of the global activities of Siemens and called for an investigation into whether the company was "fit and proper".
The unions confirmed they now planned to take legal advice from a specialist QC over a possible challenge to the government's decision.