Alinghi have accused BMW Oracle of having a French-designed yacht as part of the Swiss team's defence in a long-running legal battle over the rules for the 33rd America's Cup.

"Affidavits from a number of leading experts in the field of yacht design ... support the fact GGYC's (Golden Gate Yacht Club) trimaran is in fact a French-designed boat and not American," holders Alinghi said.

"In addition (GGYC's) BMW Oracle yacht is not even a sloop, propelled by sails, with a main and a jib, as declared in the American club's certificate of challenge, but a wing-mast rig."

Regulations, as defined in the 'Deed of Gift' that govern the race, state yachts must be constructed in the country they represent.

BMW Oracle, who race under GGYC's colours, have taken out a lawsuit in the New York supreme court arguing Alinghi are using sails constructed in the US.

Alinghi contest the claim, saying their sails are made in Switzerland, and that sails are outside the original definition of what constitutes the yacht or vessel.

They have countered that if the court backed BMW Oracle's definition of the rules, that would also invalidate the American challengers' yacht.

The head-to-head, best-of-three showdown is scheduled to start on Feb. 8 in Valencia.