Australia and South Africa on Sunday jointly called for an end to the International Monetary Fund's top job being allocated on the basis of nationality, saying it undermined the group's legitimacy.
The IMF is seeking a new managing director after the resignation of France's Dominique Strauss-Kahn, who is fighting sexual assault charges in the United States.
Under a long-standing arrangement between Europe and the US, a European has always held the key IMF job while an American leads its sister institution, the World Bank.
But Australian Treasurer Wayne Swan and South African Finance Minister Pravin Gordhan, co-chairs of the G20 IMF Reform Working Group, said the appointment of Strauss-Kahn's successor must be based on merit.
"For too long, the IMF's legitimacy has been undermined by a convention to appoint its senior management on the basis of their nationality," they said in a joint statement.
"In order to maintain trust, credibility and legitimacy in the eyes of its stakeholders, there must be an open and transparent selection process which results in the most competent person being appointed as managing director, regardless of their nationality."
French Finance Minister Christine Lagarde has emerged as Europe's choice to lead the IMF, with Britain backing her on Saturday.
Developing countries have not coalesced behind one individual.
Names mentioned include Indian planner Montek Singh Ahluwalia, Mexican central banker Agustin Carstens, former South African finance minister Trevor Manuel, and Leszek Balcerowicz, the pioneer of Poland's transition from communism to the free market.
The institution has said the nomination process would run from Monday until June 10, with the aim of completing the process by June 30.
Swan and Gordhan said it was imperative to get a new leader in place quickly.
"The task is urgent given the current challenges facing the global economy, including in particular the needs of low income and developing countries who rely on the IMF for support," they said.
"The global financial crisis demonstrated that the world needs a strong IMF and a strong managing director."
Strauss-Kahn resigned on Thursday, five days after being arrested in New York on charges of sexually assaulting a hotel maid. He has protested his innocence and said he wants to devote all his energy to fighting the case.