Barack Obama faced potential damage to his campaign yesterday after television networks aired footage of sermons by the former pastor of Obama's church likening the Democratic frontrunner to Jesus and declaring: "God damn America."

In the sermons the Rev Jeremiah Wright, who presided over Obama's marriage and provided the title of his book Audacity of Hope, condemned what he described as a systemic effort to keep black people in poverty.

The accusations of racism could prove embarrassing to Obama who has based his candidacy around a message of unity. In his sermons Wright reportedly refers to the US as being under the influence of the Ku Klux Klan, and describes black Republicans as sellouts.

"The government gives them the drugs, builds bigger prisons, passes a three-strike law and then wants us to sing God Bless America. No, no, no, God damn America, that's in the Bible for killing innocent people," he said in a 2003 sermon which was aired by ABC television.

"God damn America for treating our citizens as less than human. God damn America for as long as she acts like she is God and she is supreme."

Obama has been a member of the congregation of Wright's Trinity United Church of Christ in the south side of Chicago for nearly 20 years.

The pastor's sermons are available for sale at the church and both ABC and Fox News broadcast the addresses.

In January, Wright spoke from the pulpit in praise of Obama's leadership, comparing his campaign to Jesus's struggles under the Romans, according to Fox television. "Barack knows what it means living in a country and a culture that is controlled by rich white people," Wright said. "Hillary would never know that." He went on: "Hillary ain't never been called a nigger. Hillary has never had a people defined as a non-person."

Wright also took issue with the idea that Bill Clinton was a friend to African-Americans. "Hillary is married to Bill, and Bill has been good to us. No he ain't. Bill did us, just like he did Monica Lewinsky. He was riding dirty."

On the Sunday following 9/11, Wright described the attacks as retribution for the bombing of Hiroshima, America's policy in the Middle East, and apartheid in South Africa. Obama has told reporters he was not in church that day. Wright retired from the church last month.

Obama's campaign told ABC that he did not think of his pastor in political terms.

"Senator Obama does not think of the pastor of his church in political terms. Like a member of his family, there are things he says with which Senator Obama deeply disagrees," a statement said.

Such disputes are not exclusive to the Democrats. John McCain, the Republican nominee, is under pressure to repudiate a televangelist supporter, the Rev Rod Parsley, who has spoken of a clash of civilisations between Islam and Christianity.