Unite, Britain's biggest union, has welcomed reports that Bombardier's Derby site has been secured for three years but warns that the coalition government should not be let off the hook.
Britain's last train maker needs a significant contract for the company to have a long-term future.
The plant was under review after the Tory-led government controversially awarded a £1.6 billion order for the Thameslink route to a consortium led by Siemens.
Unite general secretary Len McCluskey said: "This is good news but it should not let the government off the hook. If the coalition had done the right thing and awarded Bombardier the Thameslink contract the company would have years of work, instead of being given a brief respite."
"Britain's last train-maker needs to win a significant contract for it to have the long-term future it deserves. The government must to everything possible to support this strategically important manufacturer. Unite will keep fighting for the future of British train manufacturing."