Bayern Munich board member Karl-Heinz Rummenigge said Newcastle United were "idiots" for meeting VfB Stuttgart's asking price for Nick Woltemade after they stumped up a reported 63 million pounds for the German striker.
Bayern had also been interested in signing the 23-year-old but dropped out of the running due to the fee quoted by their Bundesliga rivals.
"I can only congratulate those in Stuttgart that they — and now I will use inverted commas — found an idiot who will pay that much money," Rummenigge told BR broadcaster.
"Because we would have certainly not done that in Munich.
"We should not meet any demand to make someone happy, especially those financiers in Stuttgart."
Woltemade, capped four times by Germany, has scored two goals in five appearances since joining the Premier League side.
In response to Rummenigge's comments, VfB Stuttgart CEO Alexander Wehrle told Bild newspaper on Monday: "We are always happy when we get congratulations from Munich."
Reuters has requested comment from Newcastle.