"We have taken the position that we must challenge and appeal against the decision made by the court to give Madonna an interim order to adopt a child from Malawi," Justin Dzodzi, chairman of the Human Rights Consultative Committee.
He said his panel, an umbrella organisation of 67 rights groups, had agreed in principle at a meeting in Blantyre to launch the challenge before a consitutional court in the administrative capital Lilongwe.
"We will be raising constitutional issues in our challenge because under our law, a person who is not resident here cannot adopt a child who is resident in Malawi," said Mr Dzodzi.
"Malawi does not accept cross-border adoption and the alternative for Madonna is that she has simply to be a Malawi resident first before adopting, or find other means of assisting the child without adopting him."
Madonna was granted the interim order to adopt the toddler, David Banda, by the high court in Lilongwe last Thursday after spending a week in the poverty-stricken southeast African country.
Under Malawian law, expatriates adopting a Malawian child usually have to live in the country for 18 months and are monitored by social workers before they get full adoption rights.
The US diva Friday left Lilongwe on a private jet without David as officials were still to resolve passport and visas issues. The boy, whose father Yohane is an illiterate farmer, will be reunited with Madonna later.
Madonna, who was in Malawi to inspect a five-million dollar ($A6.6 million) project for AIDS orphans, left addresses in London and Los Angeles where officials can reach her and monitor the boy's progress to conform with the conditions of the order.
The singer, who already has two children of her own, must return to this country for the adoption to be finally approved.
In an interview with Britain's Mail on Sunday newspaper, Yohane Banda said he had agreed to the adoption as it was "a very good opportunity for David to get an education and grow up healthy."
David's mother died shortly after childbirth.