Former Prime Minister Helen Clark will be named today as head of the United Nations Development Programme (UNDP), according to reports.

The post, to be taken up in August, is the third most senior UN role and would involve overseeing a $US5 billion ($8.9 billion) budget, which is mostly spent on programmes in Africa.

Political newsletter Trans-Tasman reported the appointment today and TV One said it had confirmation. A spokesman for Helen Clark, prime minister from 1999 until 2008, would not comment this morning.

If Helen Clark has secured the job, it would be the highest international post held by a New Zealander since Mike Moore was Director-General of the World Trade Organisation.

Her appointment would spark a by-election in her Mt Albert electorate and would require Labour to find a new foreign affairs spokesman.

Helen Clark is known to have had a long-term interest in a UN job.

Highly placed sources told Trans-Tasman UN Secretary-General Ban Ki-Moon would confirm the appointment within the next few hours.

The National-led Government supported her nomination, with Prime Minister John Key lobbying and encouraging the Ministry of Foreign Affairs and Trade to support it at overseas missions.

Earlier, Helen Clark gained a place on the shortlist of three but then major donors to the UNDP threw their support behind her.

It was expected she would take up the post later this year, with a by-election needed in the Mt Albert electorate she has held since 1981.

UNDP is the UN's global development network, and advocates for change and connecting countries to knowledge, experience and resources in order to build a better life.