Debenhams has warned the Welsh Government it will be forced to close its main stores unless a business rates relief holiday is granted.
The UK chancellor Rishi Sunak previously granted a year-long rates holiday to all retail, leisure and hospitality firms.
Wales said it would match the pledge but then changed the threshold.
Now the chairman of Debenhams has issued a stern warning to the Welsh Finance Minister Rebecca Evans.
A letter by the chairman said: "It is deeply regrettable that, by electing to take a different approach to that taken elsewhere in the UK, you have made it economically unviable for us to continue trading the majority of our Welsh business.
"You have failed to understand the situation, where Debenhams Retail Limited is in administration and will cease to pay business rates unless it chooses to reopen its stores in Wales.
"It will be unable to reopen its stores unless you reverse your decision."
The business rates decision affects Debenhams' biggest stories in Wales; Cardiff, Swansea, Newport, Wrexham and Llandudno.
The closures would affect around 900 staff.
In April Debenhams confirmed it formally entered administration.
It is the second time Debenhams, which employs around 22,000 staff, has entered administration in the past 12 months.
The staple of the high street has 10 stores in Wales.
Debenhams' 142 UK stores remain closed in line with government guidance and the company said it would work to "re-open and trade as many stores as possible" when restrictions were lifted.
A Welsh Government spokeswoman said: “We decided to limit the Non-Domestic Rates (NDR) Relief for the hospitality, retail and leisure sector announced to exclude the small proportion of properties with a rateable value of over £500,000.
"This affects fewer than 200 properties across Wales but releases more than £100 million towards our Economic Resilience Fund – enough to support more than 2,000 businesses with grants of £50,000. The Economic Resilience Fund will support businesses of all sizes, but especially micro, small and medium sized, in responding to the pandemic and received 6,000 applications within the first 24 hours of opening."
