US Republican presidential candidate Mitt Romney told the annual NAACP convention today that he will oppose marriage equality, despite the civil rights group’s board of directors endorsing the right of gay people to marry.

According to reports, Romney received applause for his promise to “promote strong families and defend traditional marriage” if elected.

The NAACP’s board of directors voted to support marriage equality at their quarterly meeting in May. NAACP president Benjamin Todd Jealous said it was the “legacy and responsibility of the NAACP to speak up on the civil rights issue of our times”.

In the same speech, in which he appealed to African-American voters, he emphasised that he would represent Americans of “every race, creed and sexual orientation”.

Referring to marriage equality, the Republican contender said: “Any policy that lifts up and honours the family is going to be good for the country, and that must be our goal. As president, I will promote strong families and I will defend traditional marriage.”

Romney spoke mainly about the US economy, although his pledge to repeal the healthcare reform act attracted boos.

In March, leaked confidential documents written by a leading anti-gay group suggested a strategy to create hostility between black and gay voters.

The documents, circulated by the LGBT rights group Human Rights Campaign, were marked “confidential” and contained details of the internal strategy of the National Organisation for Marriage.

An internal report on the 2008 and 2009 campaigns, in a section titled “Not a Civil Rights Project” stated: “The strategic goal of this project is to drive a wedge between gays and blacks – two key Democratic constituencies”.

It continued: “Find, equip, energise and connect African-American spokespeople for marriage, develop a media campaign around their objections to gay marriage as a civil right; provoke the gay marriage base into responding by denouncing these spokesmen and women as bigots”.