A Government minister has slammed New Zealand's rugby bosses over the scheduling blunder that could force fans to miss out on watching one of the country's two top teams this weekend.

Justice Minister Kiri Allan took to Twitter on Wednesday, saying she would be supporting the Black Ferns in their World Cup quarter-final clash with Wales on Saturday - rather than watching the All Blacks against Japan

The Black Ferns' bid to defend their World Cup title rolls on in Whangārei, with the knockout clash kicking off at 7.30pm - while the All Blacks' test gets under way from 6.50pm in Tokyo.

Allan called the clash "disgraceful', citing the recent Fifa Women's World Cup draw as an example of scheduling done well.

"I'll be supporting our Black Ferns this weekend in Whangarei. But NZ Rugby, this clash was avoidable, and frankly, disgraceful. For tips on how to plan a world standard womens World Cup, suggest you take some tips from @FIFAWorldCup who set the standard last w/e w their draw."

Kiri Allan Photo / Mark Mitchell

NZR has since apologised for the clash, admitting the Black Ferns' possible quarter-final wasn't taken into consideration when scheduling the All Blacks fixtures.

"Unfortunately, when Japan Rugby set the kick-off time for the All Blacks test, NZR did not take into account the Rugby World Cup stipulation that the host nation would play in the quarterfinal 2 time slot regardless of pool results and may inadvertently cause a clash," NZR said in a statement.

"New Zealand Rugby is delighted with how New Zealanders have embraced not only the Black Ferns but the tournament as a whole."

Black Ferns assistant coach Wes Clarke earlier said fans would have a tough choice to make.

"If you're at home, you're probably going to have to make a decision which one to watch on delay, to be honest," Clarke said.

"We're conscious of the fact we're trying to play an expansive, attractive game that's going to pull people into the women's game, and that's what you're going to see if you pick us."

Veteran halfback Kendra Cocksedge added: "At the end of the day we're playing some really good footy, and we've attracted an awesome crowd across the country and across the world. We're hoping everyone gets in and supports us, and we're asking that of New Zealand and the world.

"There's been some good footy on display. Get in and support us, and watch the All Blacks on replay."

Should the Black Ferns topple Wales in the rematch – a team they beat by 44 points during pool play – they will meet either France or Italy in the next stage, with England on the other side of the draw.

The All Blacks, meanwhile, have been hit by the unavailability of several players - including the Barrett brothers, Beauden, Jordie, and Scott - through injury and bereavement ahead of their northern tour.