A new poll has found that voters in the US are evenly divided on whether or not same-sex couples have the right to marry under the US Constitution.

The Washington Post/ABC poll which was released on Friday found that 50% of respondents agreed that the Equal Protection clause means same-sex couples should be allowed to marry, 43% said it does not, and the remaining 7% said they were unsure.

In those states which still ban same-sex couples from marrying, 45% of respondents said gay couples have constitutional protection and 48% disagreed. Despite this, half still said same-sex couples should be able to marry.

Across the whole of the US< 56% said they supported same-sex marriage, and 38% were in opposition.

The largest group opposed to same-sex marriage, as shown in many polls, were those over 50 years old, and in the 18-29 group, over three quarters supported the right of gay couples to marry.

Since the US Supreme Court last year struck down a key component of the federal Defense of Marriage Act (DOMA), challenges have been intimated in many states, and only one, North Dakota, currently has an unchallenged same-sex marriage ban.