Voters in North Carolina have approved Amendment One, which introduces a constitutional ban on gay marriages and outlaws even civil unions.

The amendment reads: “Marriage between one man and one woman is the only domestic legal union that shall be valid or recognized in this State.” In effect, this bars the state legislature from giving legal recognition to civil marriage, civil unions or other forms of legally recognised partnerships to gay couples.

Yesterday, more than half a million voters received an automated telephone call from former President, Bill Clinton, where he pleaded for voters not to pass the legislation.

The message is seen as a tactical approach to the issue, did not even mention the word ‘gay’ once. Rather, Mr Clinton says it will affect the state’s “ability to keep good businesses, attract new job, and attract and keep talented entrepreneurs.”

He adds that the amendment, which outlaws all legal protection and benefits for couples outside heterosexual marriage, would gravely affect children, and prevent women from seeking help under domestic abuse. This amendment is not about keeping the definition of marriage, he said, and refers to the fact that North Carolina already has an addendum that bans equal marriage.

Catherine Bessant, global techology and operations chief of Bank of America had previously said that the amendment “has the potential to have a disastrous effect on our ability to attract talent and keep talent in the state of North Carolina.”

The vote comes after months of bitter campaigning by both the religious right and by gay rights activists, but it is thought that the endorsement of the amendment by the evangelist Billy Graham boosted the anti-equality cause considerably. Mr Graham’s letter of support for the amendment appeared in newspapers around the country. The amendment also saw statement of support from Newt Gingrich, who has since bowed out of the presidential race.

The results of the poll are expected to be also a measure of Mr Obama’s popularity in the state.

PinkNews.co.uk is backing a global social media campaign to support marriage for gay and straight couples. Out4Marriage asks supporters to record a video and upload to YouTube ending with the words “I’m coming Out4Marriage. Are you?”