Referees will have the option to show a '20-minute red card' during the autumn internationals as the concept comes to the northern hemisphere men's Test rugby for the first time.

While teams will still lose a player for the rest of the match in case of "deliberate and dangerous" foul play, technical offences - such as accidental head contact - can now be punished with a player being sent off, but replaced by a team-mate off the bench after 20 minutes.

The French Rugby Federation came out against the possibility of the 20-minute red card entirely replacing permanent removal of players earlier this week, saying such a move would be an "unacceptable step backwards" for player safety.

"No trial or subsequent change is considered without utter confidence that player safety and welfare is front and centre," said Julie Paterson, chief of rugby at organisers Six Nations Rugby.

"First and foremost, we need to look after the players and their interests, and the trials we have opted to use this November deliver on this commitment.

The Irish Rugby Football Union says like the French it does not support 20-minute red cards replacing permanent red cards entirely and welcomed the retention of the more severe sanction for the autumn internationals.

The Rugby Football Union is believed to be considering the evidence from this autumn before taking a stance on the issue.

The possibility of the 20-minute version becoming the only red card available to referees is to be discussed at a World Rugby meeting on 14 November.

The autumn internationals will also allow referees to broadcast directly to the crowd and television audience to explain the reasoning behind a key decision, as American Football officials do, for the first time.

A 60-second 'shot clock' will also be in force for penalties and conversions, with the set-piece also under scrutiny with scrums and line-outs to be set within 30 seconds of the referee making a mark.

Everyone in rugby understands that there is a huge opportunity to capture the attention of a far broader audience, alongside catering for its existing and passionate fanbase," added Paterson.

"The law trials are just one step towards exploring this opportunity and the trials running through the Autumn Nations Series will hopefully enhance the experience for fans."

The autumn internationals begin on 2 November with England playing New Zealand and Scotland hosting Fiji.