New Zealand Rugby has revealed a communication error led to Ireland prop Jeremy Loughman being allowed to return to the field against the Māori All Blacks, despite the player suffering clear concussion symptoms.

Loughman fell backwards while attempting to get to his feet following a collision in the opening minutes of Ireland's match against the Māori All Blacks on Wednesday.

Loughman underwent a head injury assessment, which he passed, before returning to the playing field 10 minutes later. Loughman was then replaced at halftime.

The incident and process surrounding Loughman's return to the game was criticised by leading player welfare group Progressive Rugby, as well as ex-players and onlookers. Progressive Rugby labelled the way Loughman was treated as "deeply alarming", saying World Rugby was not enforcing its own rules surrounding concussion.

New Zealand Rugby (NZR) today released a statement saying a review of the incident found that correct protocol was not followed during the head injury assessment due to miscommunication between medical staff.

"NZR believes Ireland prop Jeremy Loughman should not have been allowed back on to the field during the first half," NZR medical manager Karen Rassmussen wrote.

"While NZR stands by the HIA processes in place and is satisfied that player welfare is the number one priority for medical staff at the match, we have identified a gap in communications, which meant critical video evidence was not fully accounted for as part of the Head Injury Assessment (HIA) process undertaken by the independent match day medical team."

Ireland will be hoping to bounce back from the shaky start to their New Zealand tour, their clash with the Māori All Blacks ending in a 32-17 defeat in Hamilton.

However, coach Andy Farrell said he doesn't believe the performance will impact the first test against the All Blacks on Saturday.

"I don't know if that transfers really," Farrell said on Wednesday. "There are 15 guys sat in the stand, ready to train tomorrow. Of course they will watch the game, take the lessons from that, certainly from how the Māori All Blacks played.

"I'm sure those boys feel for their teammates and that they'll prepare properly tomorrow and look forward. There's nothing like sitting and watching a live game and knowing that you've got a chance in three days' time as well so that will stand us in good stead."