Madonna fought back tears as she hit back at critics of her decision to adopt a 13-month-old African boy.
The star spoke out in a TV interview with Oprah Winfrey, which is being broadcast in the US today.
Audience members said Madonna told the chat show host that she plans to take David Banda back to Malawi once or twice a year and wants him to become a spokesman for the country.
Madonna said David's father knew that he was signing away his son permanently, despite his recent comments that he thought she was looking after him temporarily.
Brook Carter, from Miami, who was in the audience, told People magazine that the singer said of Mr Banda: "He looked at me straight in the eye and said 'I'm thankful for giving my son a future and a life because if he stayed with me I would have buried him'."
Audience member Sheryl Lewis said the star said she had acted according to the law.
The emotional singer said she could not understand why she was being criticised for wanting to do good and she hoped others were not discouraged from doing the same.
Madonna was originally set to appear on the show to publicise her new children's book, The English Roses: Too Good To Be True.
Dates with other US talk shows are set for coming days in what is sure to become a major PR offensive for the multimillionaire star.
She has been stung by criticism that she has bypassed Malawi law to "buy" a baby by offering two million dollars (£1.1 million) to help orphans in the impoverished African country.
The adoption saga took a new twist when David's father, Yohane Banda, said he only agreed to let Madonna take the little boy on the assurance from government officials that Madonna would be a temporary carer.
But Mr Banda, 32, a peasant farmer, told Time magazine that he would not fight the adoption because his son would have a better life with the star.
He said: "I don't want my child who is already gone to come back. I will be killing his future if I accept that."
But he was adamant that he had not understood what was happening when he agreed to the process.
"It is true that I was not told properly that my child will be taken for good," he told the magazine.
"You know, I am not educated so the way I was told, I thought it would be the same as keeping him at the orphanage, the only difference being that he will be kept by a rich, respectable lady and in America, which is far away.
"I never understood it as my child being taken for good."
Mr Banda gave David up to an orphanage at five weeks because he was unable to care for him when the baby's mother died shortly after his birth.
Later this week, a coalition of human rights groups will ask a judge in Malawi to review the case, claiming that the country's laws prevent international adoption, even by celebrities.Reuse content