Flanker Thomson was cited for contact with Alasdair Strokosch's head after the All Blacks' 51-22 victory over Scotland at Murrayfield on November 11. He was suspended by an independent judicial officer.
"After careful consideration and having reviewed the full written decision in the Thomson case well within the permitted 72 hours of receipt, the IRB strongly believes that the sanction of one week is unduly lenient for this particular act of foul play and not aligned with the sanctions handed down in similar cases," the IRB said in a statement.
Thomson missed the All Blacks' victory over Italy on Saturday.
The arrangements for the independent appeal hearing will be made shortly.
Australian lock Rob Simmons has appealed against his eight-week ban for a 'tip tackle' on French flanker Yannick Nyanga.
Simmons came on as a substitute during his side's 33-6 loss in Paris on November 10, and is not eligible to play again until Feb. 25, just after the start of the Super Rugby season