Major US publishers are on the verge of revolt against NPD, according to a CNN report.
The likes of EA and Activision see the group's monthly retail sales bulletins as 'misleading and potentially irrelevant'.
That's because the reports don't factor in Xbox Live, PSN or iTunes data,.
"Using NPD data for video game sales is like measuring music sales and ignoring something called iTunes," the report quotes EA corporate communications executive Tiffany Steckler as saying.
"We see NPD's data as a misrepresentation of the entire industry."
Last week, NPD's report said that retail sales fell eight per cent in the US.
In the meantime, publishers continue to grow into digital content streams to supplement and sometimes expand further than sales of boxed games.
Activision has seen huge success through Call of Duty map packs - while EA itself is forecasting that it will make $750m in digital sales revenues for the year ending March 31st, a rise of 39 per cent.
Plus, rising stars like Zynga, generates its revenues purely from online transactions within Facebook. It's been valued as over $8bn previously.
But NPD has tried to calm the grumbles, saying the report blows 'out of proportion' the situation.
Divisive analyst Michael Pachter of Wedbush Morgan also defends NPD, calling it a "gross overstatement" to write its reports off: "EA saying physical game sales don't matter is like Best Buy saying television sales don't matter."