Allan has slammed the mistake as "disgraceful" after the Black Ferns booked their place into the quarter-finals of the women's Rugby World Cup in New Zealand.

Hosts New Zealand are now due to take on Wales at 7.30pm local time on Saturday (October 29) - just 40 minutes after the men's team are set to start their first game against Japan.

"@NZRugby, this clash was avoidable, and frankly, disgraceful," Allan wrote on Twitter.

The blunder has left NZ Rugby red-faced having known since May last year that the Black Ferns would play in the second quarter-final slot once advancing from the group stage.

NZ Rugby admitted it had made a mistake with the scheduling, insisting that it did not intend to "overshadow" 15-a-side women's team's World Cup campaign.

"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 two time slot regardless of pool results and may inadvertently cause a clash," a statement from NZ Rugby read.

A last-ditch request was made by NZ Rugby to move the start time only for this to be rejected by Japan Rugby.

"We respect the reasons provided for not being able to shift the time," NZ Rugby added.

"We know the scheduling clash is not ideal, but fans are still able to watch and support the Black Ferns and the All Blacks."

Chris Lendrum, general manager for professional rugby and performance at NZ Rugby, said the organisation had only realised the mistake when the quarter-final draw was confirmed.

"It's a simple oversight that's unfortunately had bigger consequences," said Lendrum.

"We're really gutted, to be honest.

"We're like every other rugby fan in New Zealand.

"We want to watch both games live.

"We were aware of it as an organisation, but the right people weren't aware of it."

Defending champions New Zealand are looking to claim the Rugby World Cup crown for the sixth time.

The Black Ferns topped Pool A with victories over Australia, Wales and Scotland.

"If you're at home, you're probably going to have to make a decision which one to watch on delay," said Black Ferns assistant coach Wes Clarke.

"We're conscious that we are trying to play an expansive, attractive game that's going to pull people to the women's game.

"That's what you're going to see if you pick us."