Former England flanker Lewis Moody also believed the RFU was wrong not to punish Saints.
"For there to be an outcome saying he shouldn't have been allowed back on the pitch, but for the club not to have been sanctioned - what message does that send to the other clubs?," Moody told the BBC.
The CMRG, which was set up by England's governing Rugby Football Union and Premiership Rugby, which runs the domestic top-flight comnetition, made nine safety recommendations for new procedures to govern future incidents.
These were welcomed by the Rugby Players' Association (RPA) but it also felt an opportunity had been missed to send out a clear statement about player welfare.
"That George was permitted to return to the field of play in the circumstances was a significant failing," the RPA said in a statement.
"While we feel that sanctions would have sent a clear message about the gravity of concussion mismanagement, we welcome the recommendations outlined in the report.
"These must be adopted and all concussion processes be kept under constant review so that everything is done in terms of training, resource and protocol to ensure this does not happen again."
North, who has suffered several head injuries in his career, is back in training but will not now face Sale.
- AAP