Margaret Beckett will be replaced by David Miliband as DEFRA secretary, it has emerged.
Mr Miliband, who is regarded as a rising star of the Labour Party, will move across from the Office of the Deputy Prime Minister.
His previous job has been as minister of communities and local government.
Mrs Beckett is to take a new position at the Foreign and Commonwealth Office.
Mr Miliband has been MP for South Shields since June 2001.
From 1994 to 1997 he worked as Head of Policy for Tony Blair, working on the policies that helped get Labour into government.
He was then Head of the Prime Minister’s Policy Unit in Downing Street during Labour’s first term in office from 1997 to 2001.