Number eight Billy Vunipola will miss England's opening game of the World Cup with Argentina following his red card against Ireland.

Vunipola has been banned for three games but it can be reduced to two if he completes the World Rugby coaching programme on tackling.

England's final warm-up game is against Fiji this Saturday.

The World Cup in France starts on 8 September and England meet Argentina the following day.

England coach Steve Borthwick will also be without captain Owen Farrell for England's first two pool games after World Rugby successfully appealed against the decision to overturn his red card in the win over Wales on 12 August.

Officially named the coaching intervention programme, 'tackle school' is allowed to be taken once in each player's career and is intended to modify the specific techniques and technical issues that lead to illegal hits.

At a video hearing held on Tuesday, Vunipola admitted that his shoulder-led tackle that struck Porter on the head was a red card offence, triggering an automatic six-game suspension.

However, the hearing saw mitigation in his clean previous record, his immediate remorse and apology and the lack of aggravating factors, thereby reducing the ban.

Vunipola is the only specialist number eight selected in England's 33-player World Cup squad. Coach Steve Borthwick will have to use the Fiji game to look at alternatives, with Ben Earl expected to replace the Saracens forward given Tom Curry is still struggling with an ankle injury.

The decision against Vunipola means England have had a player sent off for a high tackle by rugby's new 'bunker' review system in their past two warm-up games.

Farrell became the first, having initially been shown a yellow card following a high tackle on Taine Basham.

The 'bunker' system was introduced during the Summer Nations Series to support referees in making correct decisions.

Scrum-half Danny Care says England have been working on their tackle technique every day as they look to improve their discipline.

"Billy has been through a lot in his career and has been really mature and really helpful towards the rest of the squad," said attack coach Richard Wigglesworth.

"There's no worrying about himself. He's worrying about everyone else."