The prime minister has spoken to the press about Baroness Vadera, who is to leave the government for a new role with the G20.
Gordon Brown called her "one of our best ministers" and said she will be tasked with helping to create "a new system of international economic co-operation around the world".
Baroness Vadera is one of Brown's closest advisers and her new job will be based in Downing Street. She will not receive a government salary.
The prime minister spoke about her new role to reporters in New York, where he is attending the United Nations general assembly.
"Shriti Vadera, to the benefit of Britain, is joining the G20 presidencies," he said.
"What we are trying to do is to create a new system of international economic co-operation around the world.
"It's never really happened before.
"We've had the G8, we've had all these organisations - we've got this one chance to make a huge success of international economic cooperation.
"I've asked Shriti Vadera, who is one of our great ministers, to work with the G20 presidencies - South Korea next year and perhaps another country the year after - so that Britain, South Korea and that other country can plan the G20s most effectively.
"We need one of our best ministers to do it.
"She has got the international experience to do so, and I'm pleased that she has accepted my invitation to take this job and she will be working with the G20 presidencies over the next year."
Nominally a minister in Lord Mandelson's Department for Business, Innovation and Skills as well as the Cabinet Office, Baroness Vadera has spent much of her time in Downing Street.
Before joining the government she had a successful career as an investment banker at UBS, advising on banking, capital markets, project finance and corporate finance.
In 2007 Shriti Vadera was raised to the House of Lords and took her first ministerial job after eight years on the Treasury's council of economic advisers.
Lord Davies of Abersoch, minister of state for trade promotion and investment, will take over Baroness Vadera's duties as minister for competitiveness.
Her former boss, business secretary Lord Mandelson, said she has a "real passion" for the G20 and therefore her new role is "a logical move for her and us".
He added: "She has worked tirelessly to ensure businesses, especially small businesses, are supported through the recession and emerge stronger at the other side."


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