Nottingham's biggest company, Boots, is threatening to pay nothing towards the city's new tram extension - by moving 3,000 parking spaces outside the city.
The firm could save up to £1m a year and create a financial black hole at the centre of the tram scheme by avoiding the workplace parking levy.
Boots has said it is a special case and wants talks with the city council.
But the council has said there are to be no "preferential arrangements" when the scheme begins in 2012.
The move by the Nottingham-based chemist would create a 13.5% shortfall in the parking levy revenue for the first year.
The Boots site straddles the city and county border, with 1,500 car parking spaces in the Borough of Broxtowe and 3,000 spaces in the City of Nottingham.
This means the firm would be liable to pay a levy on the spaces in the city amounting to a bill of £750,000 in the first year alone.
Boots director of public policy Peter Gibson said that unless the city council was prepared to discuss how the charge could be levied differently - because of the shift workers, part timers and employees who travel when the roads are not congested - then the "obvious option was to move the 3,000 spaces to the county end of the site".
Workplace parking levy - have your say
He said: "We have a lot of land where we could build a very cheap multi-storey car park and we could park all those cars at that end, thus avoiding having to pay anything at all in terms of a levy.
"Planning permission is all that is required - the land is there already flattened."
The scheme, under which employers with more than 10 spaces will be charged £253 from 2012, will fund part of the tram extension, refurbishment to the railway station and the Link bus network which transports workers to major employers in the city.
A statement from Nottingham City Council said: "The council has included an adjustment within its financial model to take into account that employers may potentially reduce the number of liable parking places they provide.
"This is built into our workplace parking levy income projection as outlined in the business case."