The IRB promised a revision of its disciplinary system after All Black flank Adam Thomson's one-week ban for stamping provoked a storm of protest.
Thomson is now set to miss New Zealand's Test against Italy in Rome on Saturday but will be available to play against Wales and England in the remaining international fixtures of the world champions' European tour.
The back-row forward, having been cited for "stamping or trampling" on the head of Scotland's Alasdair Strokosch during New Zealand's 51-22 victory at Murrayfield on Sunday was given his suspension after an IRB disciplinary hearing in London on Wednesday.
Former England hooker Brian Moore described Thomson's suspension as "ludicrously lenient".
And the punishment was in marked contrast to the eight-week ban handed out to Australia lock Rob Simmons by a separate IRB hearing in London earlier on Wednesday for a "tip tackle" on France flanker Yannick Nyanga during the Wallabies' 33-6 defeat in Paris on Saturday.
Thomson, unlike Simmons whom the match officials at the Stade de France could not identify as the guilty party, did receive a yellow card at Murrayfield although Scotland coach Andy Robinson was not alone in thinking the forward had been fortunate to avoid being sent off.
IRB chief executive Brett Gosper, who took up his post in June, responded to Moore's comments and similar complaints on Twitter by saying: "The IRB will review this case as it is a match under our jurisdiction.
"If we decide to take action we will make it public," he added.
Samoa centre Eliota Fuimaono-Sapolu slammed the Thomson verdict and compared it with the three-week ban he received from England's Rugby Football Union last year for tweets about Owen Farrell.
"I got 3 weeks for sarcastic tweets. So had I just rucked Farrells head I would have got only a week? Its just so comical these days," Fuimaono-Sapolu said.
Simmons, a replacement forward in Paris, received a ban of eight 'active' weeks' that took into account he was not scheduled to play immediately after the end of a Wallaby tour that sees them play England at Twickenham this weekend before Tests with Italy and Wales.
His suspension runs until February 24 and leaves Australia with just two fit locks heading into Saturday's Cook Cup clash at Twickenham.
Both Thomson and Simmons have a right of appeal.