Any 20-stone prop hoping to disguise himself as a rugby sevens speedster in a bid to secure a switch of nationalities for the 15-man game should think again after the sport's governing body said it will be alert to such dealings.

The International Rugby Board (IRB) says it is confident it will sniff out any dubious attempts to use Olympic sevens qualification matches to secure a shift in nationalities for the 15-man game - and that their system has the full backing of the IOC.

After a spate of border-hopping around the time of the 1999 World Cup, the IRB introduced rules that basically prevented anyone playing for a second country if they had already been capped for another.

However, with rugby sevens due to make its Olympic debut in Rio de Janeiro in 2016, the IRB had to amend their rules to come into line with the softer, passport-based stance of the IOC (International Olympic Committee).

The IRB and IOC consider the change to apply only to sevens but, in something of a potential loophole, it appears that a player who earned a switch in nationality via an Olympic sevens qualifying event would subsequently be technically allowed to also represent his adopted nation in the 15-a-side game.

The issue has been brought into sharp relief by the announcement of the French rugby union that they have a list of 10 foreign players who might be brought into their squad, including former England flanker Steffon Armitage, who has been plying his trade with great success in Toulon for the past three years.

Armitage, who won five England caps between 2009 and 2010, and was last season named European player of the year after helping Toulon win the Heineken Cup and French league title, has been overlooked for England selection due to Rugby Football Union rules that say overseas-based players will be selected only in extraordinary circumstances.