Spotted by the eagle-eyed Chris York over at the Huffington Post, the far-right group has used a picture of a Polish Spitfire (yes, that's the same lot that are supposedly coming over here and taking our jerbs).
Established in 1940, the Polish Air Force contributed nearly 150 fighter pilots to the Allied efforts in the Battle of Britain and by the end of the war boasted more than 19,000 airmen.
The Spitfire Britain First used is from the 303 Squadron and has the markings of renowned pilot Jan Eugeniusz Ludwig Zumbach. The red and white insignia of the Polish Air Force is also clearly visible next to the propeller (below).
The 303 Squadron was nicknamed "Kościuszko" after a national military hero in Poland who also fought on the side of the US (i.e. against the British) in the American Revolutionary War.
Not that the followers of Britain First seem to care too much - the Facebook post has nearly 6,000 likes and more than 700 shares.
And they're not the first British nationalist group to get in a muddle over their heritage. The BNP was lambasted in 2009 for using a Polish Spitfire to promote its anti-immigration campaign.