A revolutionary change to rugby union's international eligibility rules has been approved by World Rugby.

A player can move to a nation of their, their parents' or grandparents' birth, but can only switch allegiance once.

In a surprise move, the ruling was passed on Wednesday by more than 75% of the World Rugby council votes.

The governing body say the new process will "benefit players and the global competitiveness of rugby".

World Rugby chairman Bill Beaumont added: "We have listened to our membership and players and sought to update the regulation recognising the modern professional rugby environment without compromising the integrity of the international game."

The move has also been backed by the global players' union, who say the decision is the culmination of years of work with their members.

"Many players across the world will now benefit from the chance to represent the country of their or their ancestors' birth, serving as a real boost to the competitiveness of emerging nations, which in turn, will benefit the game as a whole," said International Players' Union chief executive Omar Hassanein.

However, while this will help the likes of Tonga and Samoa, with former All Black Charles Piutau among those who will switch nationality, there will be strong opposition from other emerging nations who prioritise the selection of home-grown players and will not benefit from the ruling.

From 1 January 2022, any player who meets the criteria can apply immediately for a transfer, meaning there is a possibility that in the 2022 Six Nations a player may represent the second Six Nations side of their career.