Former England winger Katherine Merchant was "absolutely livid" Abby Dow was not instantly removed for a head injury assessment in the Rugby World Cup final loss to New Zealand.

Dow received treatment on the pitch then played for another two minutes before being taken off for a HIA.

"I retired early because of concussions," Merchant said.

"We didn't know as much back then so I have no beef with anything that went on medically back then.

"However, now we know the dangers."

RFU chief executive Bill Sweeney said doctors were unsure whether Dow had been knocked unconscious by the tackle, for which Simon received a yellow card.

"Then they reviewed the footage and I think it was about a minute afterwards and they said 'No, she needs to come off and have a HIA'," Sweeney said.

Merchant, a 2014 World Cup winner with England but who retired on medical advice aged 28 after 11 confirmed concussions in 14 seasons, said Dow should have been taken off immediately.

"If you are in any doubt about whether a player has been knocked out or not - you take them off," she told the Rugby Union Daily podcast.

"Whether it's a World Cup final or not is irrelevant."

England were reduced to 14 players early in the final when Lydia Thompson was involved in a head-to-head collision with Black Ferns winger Portia Woodman.

Woodman failed her head injury assessment and New Zealand director of rugby Wayne Smith said afterwards: "I don't know if she'd remember much of the game."

England lock Zoe Aldcroft also left because of a head injury and later failed her HIA while Dow came back on after passing hers.

Merchant added: "Abby Dow would never say, 'oh I feel a bit off'. She wants to stay on that pitch and when you've had your head knocked you don't know if you feel all right or not.

"So that for me is a player welfare issue, even if you have to drag that player off the pitch - get them off immediately."

Concussion in rugby has been thrown into sharp focus with more than 185 players taking legal action against rugby union's governing bodies for negligence, claiming that playing the sport caused brain damage.