Same-sex couples married out-of-state are being denied name changes on driving licences in the US state of Tennessee.

Equal marriage has been banned both by state legislators in a statute, and by voters in the state constitution.

As a result, same-sex couples married in one of 13  states and Washington DC where same-sex marriages are recognised, are unable to have their marriages recognised in Tennessee, reports the AP.

The federal Goernment, however, recognises same-sex couples, following the Supreme Court strike-down of the Defense of Marriage Act (DOMA), and allow Social Security cards to be issued in married names.

According to the Tennessean, attorneys are currently recruiting potential couples for a lawsuit challenging the state ban on equal marriage.

According to the University of Memphis law professor Steven Mulroy, who specialises in civil liberties, said two potential legal arguments against the ban are that it violates the US Constitution’s equal protection clauses because state laws can’t discriminate, and that it violates the constitution’s full faith and credit clause, which says states must respect the judgement of other states.

Several people in same-sex couples in the state have told the Associated Press that they have been denied name changes on driving licences and concealed handgun carry permits, despite attempts at several state-run centres to change the names.

A 2010 University of Los Angeles study estimated that around 2,000 same-sex married couples were living in Tennessee. Some have estimated the number at much higher given the DOMA ruling.

Chris Sanders, executive director of the Tennessee Equality Project said: “The system we have is untenable because couples are changing all kinds of other federal documents and being given inconsistent guidance in Tennessee,” Sanders said. “The short-term fix is for couples to go to court to get a name change. And the longer-term fix is for us to go to court and challenge the marriage amendment, which is what we’re doing.”