Martin Luther King's "I have a dream"
America is to commemorate the 50th anniversary of the Rev. Martin Luther King's "I have a dream" speech (WikiCommons)

A Republican activist has said that black issues in the US are treated with less importance than those of other minority groups, such as homosexuals and immigrants, at an event commemorating the 50th anniversary of Martin Luther King's "I Have a Dream" speech.

"Blacks today, we're talking about the dream. For many the dream, for poor people, is a nightmare," said Bob Woodson, the head of Centre for Neighbourhood Enterprises.

"Everybody has come in front of them on the bus - gays, immigrants, women, environmentalists.

"We never hear any talk about the conditions confronting poor blacks and poor people in general," Woodson, who is black, said.

He made his comments at a luncheon organised by the Republican National Committee (RNC) ahead of mass celebrations in the US capital to commemorate the 1963 March on Washington.

His remarks came as the Republican party struggles to revive its appeal among black voters. It won just 6 percent of the African American vote at the 2012 elections.

Woodson lashed out at African American politicians as "moral traitors" and accused them of corruption.

The 76-year-old said that black politicians had betrayed King's philosophy with double standards over the killing of Trayvon Martin, the black teenager who was shot dead by George Zimmerman, alongside murders perpetrated by African Americans.

Some black Democratic high-profile figures such as Al Sharpton and Jesse Jackson have recently been under fire by conservatives for treating Martin's case differently to that of Christopher Lane, a 23-year-old Australian baseball player who was killed in Oklahoma by three African American teenagers.

"If Dr King were alive today, he would not just be talking about justice for Trayvon Martin but he would also give a prayer for the 18-year-old man shot in the face by two black kids, or by the World War II veteran who was beaten to death for $50. Or the Oklahoma player who was killed," Woodson said.

"Dr King, if anything, was morally consistent."

No Republican politicians are to speak at the commemoration of King's famous speech.

Former President George W Bush turned down an invitation citing health problems.

President Barack Obama will make an address and former presidents Bill Clinton and Jimmy Carter are also to take the stage.