Her comments came as the bookmaker William Hill announced the odds on the peer's bid to be mayor of London had lengthened from 3-1 to 9-2 after angry denunciations accusing him of talking "racist claptrap".
Speaking from New York, where she works as a counsellor on drugs and deprivation, Ms Fullerton, 50, said: "I will just say this. I am close to my brother and for all his success he knows a thing or two about suffering prejudice. I believe that if he is elected mayor of London, he will be good for blacks, for Asians, for whites all alike. I wish him the very, very best and I will be making no further statement."
Ms Fullerton was a bridesmaid at Lord Archer's wedding to Mary in 1966 and was later employed as a nanny to his children, William and James, before she moved to the United States. Lord Archer's children regularly visit her in New York and she has been on summer holidays with Lord and Lady Archer. Earlier in the week, William Archer said: "She practically brought me up. She is like a second mother to me."
A spokesman for Lord Archer's campaign office said yesterday that the peer would not be commenting on the matter and that Ms Fullerton wanted to be left alone.
Lord Archer's mother, Lola, and her second husband, George Watson, first heard about Ms Fullerton when she was living in a children's home in Weston- super-Mare, Somerset. Her natural mother, who was white, had been unable to look after her and had given her up to the authorities. Lord Archer's family fostered and later adopted her.
Despite the odds, bookmakers yesterday reported a flood of betting on Lord Archer, with most punters seeming to take the view that despite his comments he is still the best bet to win the race for the mayoralty.Reuse content