The Social Democratic Party of Germany (SPD) has endorsed gay marriage.

The SPD is Germany's oldest and second largest political party. Prime Minister Angela Merkel's Christian Democratic Union of Germany (CDU) is the country's dominant party.

At its recent three-day national annual conference held in Berlin, the Social Democrats unanimously agreed to oppose the nation's ban on gay and lesbian couples marrying.

“The SPD is committed to opening up marriage for same-sex couples. Marriage – as a social institution – must include heterosexual and homosexual couples,” the party's resolution reads in part.

Party leaders also agreed to support giving gay and lesbian couples the right to jointly adopt children.

Germany currently recognizes gay and lesbian couples with civil partnerships, which gives couples most of the rights and protections of marriage, except joint adoption and full tax benefits.

“The SPD has given a clear signal for the full equality of gays and lesbians in society,” said Ansgar Dittmar, the national chairman of lesbians and gays in the SPD (Schwusos). “There is today no more legitimacy for the two parallel institutions of marriage and civil partnership. The SPD has again proved that it is the party of progress and social development.”

The Greens party, the nation's fourth largest, also supports full marriage rights for gay couples.

According to a 2006 Angus-Reid Global Monitor poll, a majority of Germans (52%) support the legalization of gay marriage.

(Related: Australian Labor Party votes to back gay marriage.)