Red Bull Racing will have to make changes to the floor of their cars ahead of next weekend's Canadian Grand Prix, after the FIA, F1's governing body, ruled that the holes towards the rear of the RB8 are illegal.

There was speculation there might be a protest last weekend following the race in Monaco, with Ferrari and McLaren both reported to have questioned the legality of the holes, but neither team took any action. On Friday though, race director and technical head Charlie Whiting sent all the teams a directive, confirming that such holes are now prohibited.

"Following on from a number of discussions in Monaco, during which it became clear that certain misunderstandings existed, we feel it would be helpful to make our position clear," the note read according to Reuters.

"It has been argued that, as it is not explicitly stated that fully enclosed holes cannot be located in a surface lying on the step plane rearward of a line 450mm forward of the rear face of the cockpit template, then they may be located in such areas.

"We disagree with this view and consider it implicit that fully enclosed holes may not be located there.

"If they were permitted the opening part of the second paragraph of Article 3.12.5 (which was added to the regulations at the same time as Articles 3.12.9 and 3.12.10 for 2011) would be superfluous."

Speaking prior to last weekend's race in Monaco, Red Bull team principal, Christian Horner was adamant there was nothing illegal about the car. Indeed when the holes in the floor first appeared in Bahrain, the RB8 was declared legal, with the both Red Bull cars successfully passing scrutineering at every race that followed - including Monaco.

"There was a fuss after Bahrain but it was clear that the car complied," Horner told Sky Sports F1. "We sought further clarification on that and are happy that the car is compliant. The car is the same in that area as it has been in Barcelona and Malaysia.

"We are comfortable the car complies with the regulations and we are not going to change it."

Red Bull has yet to issue any sort of response following the FIA's change of heart, although it should be noted that the ruling will have no effect on the previous results, including Webber's recent win at the Principality.