The Sports Direct and House of Fraser owner said that the £2 million cap on the amount of relief a company can claim means it will have to review all its stores to find any that might no longer be viable.
A judge issued a winding up order against department store Debenhams in January, and the company’s administrators have been selling off parts of the business.
Debenhams has major sites in Preston, Blackpool and Wigan.
Online retailer Boohoo bought the brand name and its website for £55 million later that month.
However, it did not want Debenhams’ 118 shops.
Mr Ashley is reportedly trying to take over some of those stores, a move which could create jobs.
On Wednesday the Chancellor extended the holiday on business rates, a tax which all shops and pubs must pay, until the end of June. An original relief package was due to run out at the end of this month.
The Chancellor said that for the rest of the financial year after June rates would remain discounted by two thirds, up to a value of £2 million if businesses are closed.
This cap shuts out many larger businesses, including Mr Ashley’s Frasers Group, and disappointed those hoping for a wider overhaul to the tax.
“Frasers Group wishes to note its disappointment at the business rates relief announced,” the business said today (Friday).
“Whilst the retail industry as a whole has repeatedly asked for structural reform of business rates, none has been forthcoming. Frasers Group and many retailers would have expected suitable relief until structural reform is implemented.”
It added: “For Frasers Group this cap will make it nearly impossible to take on ex-Debenhams sites with the inherent jobs created. It will also mean we need to review our entire portfolio to ascertain stores that are unviable due to unrealistic business rates.
“Frasers Group believes that retailers should pay the fair amount of rates in line with realistic rateable values, but instead we continue to have an unwieldy, overly complex, and out of date business rates regime.”