Wellington - World Rugby has confirmed it has introduced rules which ban players from writing messages on strapping worn on their wrists in matches in the Sevens World Series.

The move was revealed by New Zealand players who said they had been warned they could be fined up to $1 000 for breaking the rule which bans the appearance of any messages - personal, religious or political - on strapping tape.

The New Zealand Rugby Players Association said on Wednesday the rule was "buried" in a participation agreement signed by teams ahead of the season-opening tournament in Dubai and had not previously been announced to players or national rugby unions.

World Rugby has defended the move, saying it is necessary to make sevens rugby compliant with International Olympic Committee regulations which ban athletes from wearing any unauthorized slogans, logos, messages or symbols. Sevens became an Olympic sport for the first time at last year's Rio de Janiero Games.

"There has been a significant increase in strapping art or messages in the series in recent seasons which is impossible to police for inappropriate or political statements by the match officials in the short period of time before entering the field in a sevens environment across multiple matches and in multiple languages," World Rugby said in a statement.

"While World Rugby recognizes that the overwhelming majority of the messages are appropriate and that is something that the players enjoy doing, there have been a small number of occasions where messages have gone unchecked and caused offense to teams, nations, commercial partners etc.

"This is a common-sense approach that has been accepted by all participating teams."

But NZRPA chief executive Rob Nichol said the ban was "poorly implemented" and he would work to have it repealed.

"I think the whole process that's been around it has been poor," Nichol told Fairfax media. "It hasn't gone out for consultation and that's a big problem.

"It makes the game and themselves look a bit stupid. By just unilaterally making this decision and then imposing it on the athletes, that's just completely contrary to the values and the character of the game."

Nichol said he did not believe the writing of messages on strapping tape was a major problem as most messages were of a personal, not a political nature.

"From a rugby perspective, how prevalent is it?" he said. "I'd say 99.9 percent of athletes that do it, there is nothing wrong with what they write."

All Blacks prop Kane Hames was censured last year for writing a message on wrist strapping which supported Native Americans protesting against the routing of an oil pipeline through tribal lands.