A Democratic lawmaker is joining dozens of Republicans who want to ban same-sex marriages in the US Constitution – even though there efforts are unlikely to succeed.

US Representative Nick Rahall of West Virginia is the first Democrat to sign on to the proposed Federal Marriage Amendment (FMA) introduced by Republican Representative Tim Huelskamp shortly after the Supreme Court struck down Section 3 of the Defence of Marriage Act (DOMA) last month.

The amendment would define marriage as being between a man and a woman inside the United States.

The bill to create the FMA still only has 39 sponsors, and none of those are senior members of the GOP House membership.

It is unlikely to gain significant political traction following June’s Supreme Court ruling.

On Thursday, GOP leaders indicated in legal documents that they had even stopped defending laws that prohibit the federal recognition of legally married same-sex couples and their rights.

A spokesman for the Human Rights Campaign said Mr Rahall must have “a fondness for being on the wrong side of history.”