In a new Cabinet that sees former Secretary of State for International Development Andrew Mitchell make a coveted move to Chief Whip, there is now a risk that the momentum Mitchell brought to DfID may be halted.

Mitchell has had his critics, both within government and from NGOs, but he has undoubtedly brought focus to the Department along with his view that poor countries should aim to grow their way out of poverty. He has recalibrated efforts towards helping the very poorest in society and increased transparency through his value for money and results orientated agendas. Other notable achievements on Mitchell's watch include the establishment of the Independent Commission for Aid Impact and the creation of a new department within DFID aimed at private sector engagement. It could well be the steel Mitchell showed in maintaining the government's commitment to 0.7% GNP spending on aid and his defence of the department's ring-fenced budget that proved attractive to David Cameron, who is seeking to mollify disquiet on the Tory backbenches.

With Justine Greening now at DfID it is unlikely there will be an ideological change in the prominence that economic growth strategies will play in addressing global poverty. Without question, there is a role for growth-focused development. The movement out of poverty for millions of people over the last decade is closely linked to phenomenal rates of growth in China, many other parts of Asia, and Africa. But such growth has come at a cost, in terms of carbon emissions and other forms of industrial pollution, as well as harsh labour conditions.

The International Labour Organisation, in their latest estimate, put the number of people working in 'forced labour' at 21 million, 74% of which takes place in Asia and Africa. Modern slavery may not involve literal chains but the shocking rates of those in forced labour is compounded by the conditions faced by millions of other workers, conditions which the UK began to legislate against at home more than 150 years ago with the first Factory Acts of the Industrial Revolution. The key challenge for Greening, therefore, will be to ensure future growth in the poorest parts of the world is both environmentally sustainable and morally acceptable.

A good starting point for the new Secretary of State will be to pick up the aspirations of the UN Rio +20 Earth Summit of June this year, to develop a new set of sustainable development goals, and work closely with the Prime Minister as he co-chairs a high-level UN panel on the post Millennium Development Goals framework. The aim should be to ensure the avoidance of parallel processes and the achievement of a new development paradigm that has sustainability at its heart.

Greening's move to Secretary of State for International Development may have been driven by a desire to eliminate impediments to a third runway at Heathrow, but her demonstrated ability to fight a corner will be of great use. The department's ring-fenced budget is likely to be now both besieged and directly attacked as austerity measures invite increasing unpopularity with election timetables drawing closer. Greening has proved she can stick to her guns regarding aviation policy and it is hoped that such strength can now be applied to her new brief.

It has never been easy to address issues of global poverty. Genuine solutions require long-term commitment and courage in making domestically unpopular decisions. Greening, it appears, could well have what it takes to make a meaningful impact on the lives of the poorest people in the world. In addition, she need not face these challenges alone. Working through the United Nations can help achieve international political consensus on development priorities and strategic implementation through agencies and programmes. The new Minister would therefore do well to seek early appointments in New York and Geneva so that she can quickly develop her understanding of the tasks ahead and the opportunities the UN brings to address them.