Union leaders will spend this weekend drawing up an alternative business plan to prove Peugeot's Ryton plant can still have a viable future.
Representatives from Amicus and the Transport & General Workers Union will present their proposals to management at the factory in a last ditch attempt to save it and its 2,300 jobs.
The battleplan was being formulated as Lord Bhattacharyya, head of the Warwick Manufacturing Group said it would have been "pointless" Peugeot reinvesting in the Coventry site.
But Roger Maddison, national officer for Amicus, said: "We have our own research department which will be looking at the business case for keeping Ryton open.
"Peugeot may say it is expensive, but they cannot say it makes losses because that would be a lie.
"General Motors would love to have a factory like Ryton which makes a profit, as would Ford. We have a few days to do this and we will present it to the company next week."
Jim O'Boyle, works convenor at Ryton for the T&G said: "We want to have proper, meaningful consultation with the management.
"That means they outline their ideas and exchange ideas. We should have been given the opportunity to consult before being presented with a fait accompli."
But as workers returned to the plant yesterday, Lord Bhattacharyya said he would have taken the exact same closure decision had he been in management's shoes.
Lord Bhattacharyya, an adviser to the Government, said he was in some ways surprised that the ageing 206 model built at the factory had lasted as long as it had.
He said: "If I was in their shoes I would do the same thing. It is sad, of course, and the workers need to find jobs quickly, but Coventry is doing pretty well." Unemployment in the area was low and both the high tech and service sectors were doing well.
Lord Bhattacharyya said Eastern Europe was a huge market and he could understand why Peugeot was instead investing its money in Slovakia which has good engineers and a skilled workforce.
Peugeot was looking to build an infrastructure for the East European region. "It is a huge market - standards of living are going up."
Lord Bhattacharyya said Ryton was a small plant by the standard of car factories and was making just the one model.
It would have required huge investment to put a replacement in. And with most components coming from France, and the growing market being in Eastern Europe, there was no sense in making a new model in Coventry only to have to ship it back to the Continent.
"Logistically it is not the right thing to do," said Lord Bhattacharyya.
He denied that the labour bill would have played a major role in the decision, saying this represented only a small part of total costs.
The unions' case is boosted by a claim by one leading analyst who cast doubt on Peugeot's claim that Ryton is an inherently more expensive plant than its mainland Europe counterparts - even though it is less automated.
As recently as 2003 it was the third most productive in the Peugeot empire, behind Vigo in Spain and Audnay in France, according to Professor Garel Rhys of Cardiff Business School. He calculated that at its height in 2003, Ryton produced 67 cars per worker, 24 per cent higher than Poissy, a French plant that also makes the 206, and which achieved only 54 units per worker in the same year.
"Peugeot claim it costs more to build cars here. But I would be flabbergasted if that were true," Prof Rhys said.
Peugeot, which claims its costs #267 more to make a car in Britain than in France, would not comment on Prof Rhys's statement.