Thousands of people demonstrated in support of UK train manufacturer Bombardier last weekend.
Around 10,000 workers and supporters took part in the Derby protest about the government's decision to award a lucrative contract to build new carriages to German firm Siemens, ahead of Bombardier.
Bombardier has warned that 1,400 jobs will be axed as a result of losing out on the £1.4 billion contract to build carriages for the Thameslink route between Bedford and Brighton.
The demonstrators marched through Derby city centre to a rally, where Diana Holland, assistant general secretary of Unite, called on the government to reverse its decision.
"We have created a huge alliance here and we must keep the campaign going because it is not too late to persuade the government to change its mind," she said.
"The Government last week opened up a red tape challenge on manufacturing so the only thing they have to offer is cutting workplace safety standards and employment regulations. What they need to do is support workers and invest in manufacturing."
She asked why the government had not taken social costs and jobs into account when awarding the contract, which she claimed had been structured to disadvantage the Derby plant.
Unions were continuing to press politicians to support a change of heart from the government and were considering a legal challenge, she added.
A poll of more than 25,000 adults for the Unite union showed that 88 per cent wanted the government to reconsider its decision and 95 per cent believed the coalition should actively support manufacturing jobs in this country.
"This Government strongly supports British manufacturing," said a Department for Transport spokesman.
"However, the Thameslink procurement was set up and designed by the previous Government and we are legally bound by the criteria set out at the beginning of that process.
"Going forward, we fully recognise that there is a need to examine the wider issue of whether the UK is making best use of the application of EU procurement rules and this will be examined as part of the Government's growth review."