The French firm blamed high production and logistical costs for the loss of 2,300 jobs, when it was announced Ryton would be closed yesterday.
A Peugeot spokesperson said: “We realise it is a difficult time for staff and that employees had brought about tremendous productivity improvements. However, it doesn't change the economics of the situation. Ryton is the most expensive manufacturing plant in Europe," he said.
Every car produced at Ryton costs €415 (£287) more than anywhere else in Europe, according to Peugeot.
Derek Simpson, general secretary of Amicus, said: "It is inconceivable that workers in France would be laid off on this scale.
"Weak UK labour laws are allowing British workers to be sacrificed at the expense of a flexible labour market."
Des Quinn, regional organiser for the T&G union, told BBC Five Live that it would strive to reverse the decision.
"The plant is productive, and profitable: that they've never denied," he said.
"We'll be trying our best to convince them their decision is short-sighted, unjust and to overturn it."
T&G general secretary Tony Woodley called the closure a "disgrace" and "corporate greed at workers' expense".
Ryton paint sprayer, Ian Taylor, heard the news on the car radio as he made his way to start his shift. He was sent home.
He said: "We're all gutted. They have put it down to economics which cost them too much to build the car here.
"There have been rumours flying around since a shift was cut last year so I wouldn't say it was totally unexpected."
Production at Ryton will move to a single shift in July and halt completely in mid-2007. Speculation about the short term future of Ryton is rife. Workers at the plant believe production will end before September and the site will be sold off to Coventry’s expanding airport.