Barack Obama has been in contact with his “Auntie Zeituni” since she moved to America, but the presidential front-runner said at the weekend that he did not know she was an illegal immigrant and suggested that she should leave the country.

“If she is violating laws, those laws have to be obeyed. We’re a nation of laws,” Mr Obama said in an interview yesterday with CBS News. “Obviously that doesn’t lessen my concern for her . . . but I’m a strong believer you have to obey the law.”

Zeituni Onyango, the half-sister of Mr Obama’s Kenyan father, was found by The Times last week living in a disabled-access flat on a housing estate in South Boston. She is known affectionately as Auntie Zeituni in Mr Obama’s bestselling memoir, Dreams From My Father, where he recalled that she was the first Kenyan relative to welcome him to the homeland of his father. “‘Welcome home,’ Zeituni said, kissing me on both cheeks,” Mr Obama wrote.

The Obama campaign said that he had seen her several times since that first meeting in 1988, including on a trip to Kenya with his future wife, Michelle, in 1992.

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Ms Onyango visited the family in Chicago on a tourist visa at Mr Obama’s invitation in about 1999, the campaign said, stopping to visit friends on the East Coast before returning to Kenya. She also attended Mr Obama’s swearing-in as a US senator in January 2005. She reportedly said in an interview at the time that she had been flown to the United States from Kenya for the event.

However, Mr Obama’s half-brother, George Hussein Onyango, told The Times that she moved to the US about eight years ago. The Boston Housing Authority said that she had applied for public housing in 2002 and had been given a council flat in 2003.

Asked by The Times how long she had lived in America, she said: “I have been coming to America ever since 1975. I always come and go.”

Mr Obama last heard from “Auntie Zeituni” when she called him about two years ago to say that she was in Boston, but he did not see her there, the campaign said. She apparently did not consult him when she ran into immigration troubles, even though he is a lawyer and advocate of the poor.

David Axelrod, the chief strategist of the campaign, said that Mr Obama and Ms Onyango did not have “a real close relationship”. He predicted that voters would not pay much attention to the revelation that she was living illegally in America. “I think people are suspicious about stories that surface in the last 72 hours of a national campaign,” he said.

The Obama campaign returned $260 (£161) in political contributions she had made in donations because they were illegal owing to her status.

The Republicans made no effort to turn Ms Onyango’s status into a campaign issue. Mark Salter, an adviser to John McCain’s campaign, said: “It’s a family matter.”

Ms Onyango was instructed to leave the US in 2004 by an immigration judge. Her refusal to do so would be a non-criminal violation, handled outside the criminal court system.

Her case has prompted an unusual nationwide directive inside the US Immigration and Customs Enforcement Agency requiring that any deportations before the presidential election be approved at least at the level of a regional director. The move is seen as a sign that the Bush Administration is aware of the political sensitivity of a possible deportation before polling.

The US Department of Homeland Security is investigating whether the leak about the immigration status of Ms Onyango violated its privacy rules, which bar the disclosure of information about individuals.

“They are looking into whether there was a violation of policy in publicly disclosing individual case information,” Kelly Nantel, a spokeswoman, said.

Ms Onyango was seen leaving her flat with a small bag after The Times broke the story on Thursday. A neighbour said that she was staying with relatives in New England.

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