A new Gallup poll shows that a slight majority - 54 per cent - of Americans believe that homosexuality is acceptable. Forty-two per cent say that homosexuality is morally wrong.

In an interview with The Christian Post, Frank Newport, editor in chief for Gallup, explained that support for same-sex marriage has tended to track closely with the belief that homosexuality is acceptable.

"Overall, they're very close and they've kind of followed the same trend pattern if you look over time," Newport said. "So, basically, they're both rising together and falling together and so forth."

According to the poll, 50 per cent currently say same-sex marriage should be recognised by the law as valid. In 1999, only 35 per cent said so.

Gallup has asked the question about whether gay and lesbian relations are morally acceptable every year since 2001.

In 2001, 53 per cent of Americans said that homosexuality is morally wrong and 40 per cent said it is morally acceptable. Belief that homosexuality is morally acceptable steadily increased until 2010. Since then, the numbers have remained steady at between 52 and 56 per cent.

Last week, 61 per cent of North Carolina voters supported an amendment to their state constitution that defines marriage as between one man and one woman. Thirty-one states have voted to add amendments to their state constitutions that ban same-sex marriage. In those states, even liberal-leaning states like California, those amendments have passed, many with over 60 per cent support.

There are two possible reasons, Newport said, for why there is greater support for same-sex marriage in polls than in state referendums. First, Gallup's poll is nationwide, but the referendums are isolated to individual states where support for same-sex marriage may be lower than for the nation as a whole.

Second, voting in a referendum is largely based upon turnout. Those who turn out to vote are not necessarily representative of the state as a whole. It may be that voters who do not support same-sex marriage turn out to vote in higher numbers than those who do support same-sex marriage.

A CBS News/New York Times poll released Monday showed 38 per cent support for same-sex marriage. Newport explained the different result is due to the choices offered to respondents. The CBS/NYT poll offered respondents a choice between same-sex marriage, same-sex civil unions or no legal recognition for same-sex couples. Gallup only asked respondents if they were for or against legalised same-sex marriage.