"It is a ranking that is badly done and I said it the first day I arrived at World Rugby," he said.
"It has no order, it is all mathematical and I would say that it is almost a matter of marketing.
"Argentina, for example, plays all the games with the first three [New Zealand, Australia and South Africa] and Japan or Fiji win two or three games and are above Italy who also play in a very tough tournament like the Six Nations.
"This was demonstrated when Wales never beat New Zealand in history [since the rankings were created] and now appears first.
"It's ridiculous! I'm going to change it, I assure you."
In the wake of his side's resounding victory over Australia at Eden Park in Auckland two weeks ago, All Blacks head coach Steve Hansen voiced his disapproval of the way in which his side were demoted to No 2 on the rankings for the first time since 2009.
"We won the Bledisloe Cup and lost the rankings. Ask yourself how that works," he said.
"I've never understood their system. You win a game and you lose the top ranking?
"When you sit back, it's something that's going to happen anyway – the top-ranked sides are playing each other in the northern hemisphere, and you get more points if you beat top sides.
"We just need to get ourselves in the right frame of mind to go to the World Cup and win that. I'm not too worried about rankings."
Wales host Ireland at Principality Stadium this weekend in third of their four World Cup warm-up tests.
Currently holding a 0.03-point lead over the All Blacks, a loss for Warren Gatland's side would be enough to see them fall back to second place.
Following this week's clash, Ireland and Wales will play a return fixture next week in Dublin, while the All Blacks will face Tonga in Hamilton on September 7.
World Rankings Top 10:
1 – Wales (89.43)
2 – New Zealand (89.40)
3 – England (88.13)
4 – Ireland (87.36)
5 – South Africa (86.83)
6 – Australia (84.05)
7 – Scotland (79.87)
8 – France (79.72)
9 – Japan (77.21)
10 – Fiji (76.98)
This article first appeared on RugbyPass.com and is republished with permission