The AFL have admitted a controversial free kick, awarded to Brisbane in the dying minutes of their nail-biting win over North Melbourne, was a mistake.

The decision against Kangaroos defender, Scott Thompson cost North Melbourne the game and effectively crushed whatever finals hopes that remained.

7NEWS.com.au's Tom Browne confirmed with the AFL that the decision was “incorrect”.

“The AFL Umpiring Department advises the free kick awarded to Brisbane Lions’ Oscar McInerney against North Melbourne’s Scott Thompson in the fourth quarter of last night’s match at The Gabba was incorrect,” the statement obtained by Browne read.

It's understood the AFL's position is that the mark to Thompson should have stood, considering the North defender held his ground and used his body in a legal manner.

7NEWS.com.au also understands the timing of Thompson’s contact was appropriate and it was not a push in the back.

Meanwhile, North Melbourne coach Rhyce Shaw said he didn't understand the free kick that gave Brisbane the decisive lead.

The relentless Kangaroos led until the latter stages of the third term on Saturday before Brisbane's weight of possession and field position seemingly had them on the way to a fifth-straight win.

Shaw's plucky side - chasing a sixth win from their last eight starts to keep them within a victory of the top eight - kicked two goals against the run of play to edge back in front in the final five minutes.

With scores locked approaching the final minute, Lions tall forward Oscar McInerney won a free kick against experienced Kangaroos defender Scott Thompson for an illegal shepherd.

North Melbourne coach Rhyce Shaw won't criticise the free kick given against his side. Credit: AAP

He nervelessly booted it, with Hugh McCluggage's goal after the siren ensuring a 12.15 (87) to 12.3 (75) win and outright second spot.

Multiple premiership-winning pair Cameron Ling and Dermott Brereton were among those to question the call in commentary, saying Thompson's bodywork was within the laws of the game.

Current players Steven May and Patrick Dangerfield also backed Thompson in posts on Twitter.

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Shaw was careful when responding post-game, before ultimately tipping his cap to Chris Fagan's side.

"That’s certainly a difficult one … it’s interesting he marked the ball, but the pressure of the game, the players make mistakes, everyone makes mistakes," he said.

"I’m not sure I understood it, but that’s just the way it is. I can’t do anything about it now, the game’s done.

"We gave away a lot of free kicks (in the third quarter), that were silly, undisciplined free kicks.

"That's not going to help ... and Brisbane brought the heat."

Brisbane could well have been ruing a line-ball decision of their own when North tall forward Ben Brown goaled following a contentious free kick just moments before McInerney's.

The Brisbane Lions have edged North Melbourne by 12 points in an AFL thriller. Credit: AAP

Fagan wasn't fussed though, supporting the officials and praising his side for finding a way past a valiant opponent.

The loss leaves North Melbourne two wins outside the top eight, but Shaw said that wasn't the focus.

"We play West Coast over there (next week), it's a huge challenge for us," he said.

"Yeah they (Brisbane) got us in the contest (162-133), peppered us in inside 50s (67-43); they're a top quality team but somehow we were still in the game at the end and that's a good sign."

With AAP