Sarah Palin wanted to adopt her grandchild so people would not know her 17-year-old daughter was pregnant, the father of the child has said.

In an interview with Vanity Fair, Levi Johnston said former Republican vice-presidential candidate Palin had a plan to deal with her daughter Bristol's pregnancy.

(Clockwise from left) Sarah Palin; daughter Bristol and son Tripp; Levi Johnston.

"Sarah kept mentioning this plan. She was nagging — she wouldn't give it up. She would say, 'So, are you gonna let me adopt him?' We both kept telling her we were definitely not going to let her adopt the baby. I think Sarah wanted to make Bristol look good, and she didn't want people to know that her 17-year-old daughter was going to have a kid," Mr Johnston told the magazine for its October edition. Excerpts of the interview were posted on the magazine's website on Wednesday.

Meghan Stapleton, Mrs Palin's spokeswoman, did not immediately respond to request for comment, but has previously discounted Mr Johnston's allegations. Mrs Palin has been keeping a low profile since she resigned on July 26 with more than a year left in her first term.