Barbosa has stepped down as CFO and executive director for personal reasons.
He has also stepped down as a member of the group executive committee and other committees.
As chairman of BG South America, based in Rio de Janeiro, he will provide senior counsel and advice to the BG teams in Bolivia, Chile, Uruguay, and Brazil.
BG Group chairman Andrew Gould said: "I would like to express on behalf of BG Group's Board our sincere thanks to Fabio for all his excellent work as CFO over the last two years.
"His efforts in the execution of the portfolio rationalisation programme and in diversifying and broadening our funding options and sources have been instrumental in materially strengthening our balance sheet position, helping underpin investment in, and the delivery of, our key global growth opportunities.
"As chairman of BG South America, Fabio's wealth of experience will prove important in realising the huge value inherent in our substantial interests in the region." BG Group financial controller Den Jones, - who acted as Barbosa's alternate director - has been appointed a director of BG Group plc.
Jones will continue to fulfil the role of BG Group interim CFO pending the conclusion of a succession process for the role of CFO.
That succession process will comprise both an examination of potential internal candidates and an external search.
Chris Finlayson will continue as chairman of the investment committee for this interim period.
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