British rockers The XX have taken aim at officials of a Croatian anti-gay marriage group after they used the group's song Intro in an online ad without permission.

The bandmates have released a statement distancing themselves from the U ime obitelji message, insisting they all "unconditionally" support the right to equal marriage.

The open letter posted on the group's page reads, "It has come to our attention that our music has been used without our permission in a promotional advert by the Croatian organisation U ime obitelji.

"We wish to state that we didn't, and would never, approve the use of our music by this organisation."

U ime obitelji officials are hoping to make history in Croatia this weekend (01Dec13) after collecting enough petition signatures to force a referendum on an equal marriage ban in their homeland.

Following The xx's post, the group's ad has now been removed from cyberspace.