British band The xx have issued a statement saying they do not condone the use of their music by a Croatian anti-equal marriage organisation.

Posting a statement on its Facebook, the band said they “unconditionally” support the right of same-sex couples to marry.

The online advert by anti-equal marriage group U ime obitelji, featured the band’s track Intro

“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”,” the statement posted on The xx’s Facebook page said.

“We wish to state that we didn’t, and would never, approve the use of our music by this organisation. To be clear, we unconditionally support the equal right to marriage regardless of sexuality.”

The advert has now been removed.

The organisation behind it, however, has gathered enough signatures to force a referendum on whether to ban equal marriage.

More than 700,000 people signed the recent petition to change the constitution to define marriage as “the lifelong union of a woman and a man.” The referendum will take place on 1 December.