WELLINGTON (AFP) - All Blacks coach Steve Hansen has warned rugby union risks becoming boring unless steps are taken to make the game more attacking and simplify its bloated rule book.

He said defence was dominating the 15-a-side code and detracting from the game as a spectacle.

"I don't think the game's boring yet but it could go that way," he told New Zealand's Radio Sport.

"I think we're victims of our own demise, we've got better and better at coaching defensively and, because of that, we'll have to get better at attack.

"But, at the moment, it seems to be a defensive game rather than an attacking game."

Accusations of playing boring rugby are often hurled at northern hemisphere teams by southern fans but Hansen said he was talking about trends across the entire game, not just in one area.

He said the laws of the game, which run for more than 200 pages when downloaded from governing body World Rugby's website, needed to be culled.

"One of the problems we've had over the years is that we've added rules in but we haven't deducted," he said.

"So we've got this mess and, at some point, we need to fix the mess and say 'what are the critical rules we need here and let's simplify it so people can see it and understand it and make it easier to referee?'"

Combined with the increased athleticism and speed of modern players, Hansen said hard-to-understand rules and defensive coaching were stifling attacking play.