Unions fighting the closure of Peugeot's factory at Ryton have disputed claims their rescue plan would cost 100 million euros (£69 million) a year more than shifting production to Slovakia.
A meeting is due to be held next week where Peugeot executives will spell out to the unions their alternative plan - which will involve going down to one shift - will not be viable to keep the plant open.
But last night union leaders accuses Peugeot of underestimating the damage to their sales in the UK along with the redundancy and clean up payments they would have to make before pulling out.
Transport & General works convenor Jim O'Boyle said: "What Peugeot has not taken into account are the exit costs of leaving Ryton and UK. They are underestimating these in every way.
"There will be the redundancy costs and the environ-mental costs of cleaning up the site.
"Then there is the effect on their market share."
Mr O'Boyle cited a recent report which claimed 38.3 per cent of car buyers would boycott a manufacturer which pulled its production out of Britain.
"If that happened at Peugeot we are talking about a fall of 100,000 units. This would more than offset any gains they are talking about by moving to Slovakia.
"We agree they have to reduce the costs of running Ryton, which is why we have also offered to look at other ways to make savings."
But Jon Goodman, director of communications at Peugeot, said: "The alternative plan has not been viable from day one and the unions have got to stop saying it is.
"The unions have gone from saying there is no justification in closing Ryton to saying it is going to cost more.
"The reality is that the group is facing a difficult decision. We have looked at every angle for an alternative.
"Contrary to perceptions, this is not down to corporate greed. Profits went down by 21 per cent last year, and profits from our car division make less than half of our investment in research and development.
"That is not sustainable. We have to reduce our costs. To do that we have looked at our most expensive plant and that is Ryton."
Meanwhile Ryton workers will continue their campaign to keep the plant open, with a protest outside a Citroen dealership in Rugby.