The Bavarians' vice president has continued the ongoing dispute between the two clubs over a sum of money loaned to the Signal Iduna Park side during its financial struggles.
The rift between the pair stems from a disagreement in the details of a loan that Bayern paid Dortmund in 2004, a figure reported to be 2 million euros.
Watzke had initially claimed that Dortmund would have to pay 8 percent interest on the loan, before retracting the statement following fierce denials from Hopfner, who protested the rate of repayment was much lower.
"I have not insulted him, but placed only the facts on the table,” Hopfner said to Kicker.
When questioned whether there would be any apologies, Hopfner replied: “Certainly not, absolutely not."
Despite admitting his initial error, Watzke went on to refute claims that Bayern’s loan saved Dortmund and aided its recovery from past financial problems.
Speaking to Welt am Sonntag, Watzke said: “Bayern have given a loan to my predecessor in the previous year, and in February 2005, BVB was insolvent. So there you go: Where have Bayern Munich contributed something to the rescue?"
Hopfner, who is currently interim president, will officially replace Uli Hoeness on May 2, after he was given a jail sentence in March for tax evasion.