Liberian Registry chief executive Scott Bergeron says the joke is on Nautilus International after the ­union poked fun at the shipping flag’s 70th-anniversary celebrations.

Nautilus International general secretary Mark Dickinson, writing on Twitter as @Mdickinson1262, tweeted his thoughts on the registry’s anniversary poster, printed to coincide with Posidonia. The poster proclaims: “All flags are not alike.”

“Cracking bit of ironic marketing by the Liberian registry,” Dickinson wrote.