A rail union has warned that as many as 13,000 jobs could be at stake in and around Derby due to Bombardier losing out on a £1.4bn government contract.
The firm is planning to shed more than 1,400 jobs after failing to win the contract to build Thameslink carriages.
Rail union RMT said thousands more working for companies which supply Bombardier may also be affected.
The union has organised a mass demonstration on 23 July in the city in protest at the plans.
Canadian owned Bombardier lost out to German group Siemens as the preferred bidder to build 1,200 carriages for the route between Bedford and Brighton.
The firm said due to this, and other contracts coming to an end, 446 permanent jobs and 983 temporary contract staff would be cut.
RMT general secretary Bob Crow said: "On the 23rd July we intend to bring the whole of Derby out onto the streets in protest at plans that would destroy core manufacturing industry and 13,000 jobs in and around the city.
"This act of political vandalism would impact on every single person in the area.
"If the government and their puppet-masters in the EU think that the fight for the future of Bombardier is over then we've got news for them - it has only just begun."
The government has said that the Siemens bid represents the best value for money, and that it was following EU procurement rules, which do not allow where companies are based to be taken into account.