Helen Clark is stepping down from her position at UN

Former Prime Minister Helen Clark has told the UN she will step down as head of the UNDP when her term ends in April.

Clark sent a letter to staff this morning to advise them of her decision not to seek another term.

"It has been an honour and privilege for me to lead UNDP for eight years," Clark wrote in the email addressed to "dear colleagues."

She was appointed in April 2009 and her role was renewed in 2013 for a second four year term.

Clark unsuccessfully ran to be Secretary General of the UN earlier this year - but Argentina's Antonio Guterres was selected for the role instead.

Former British foreign secretary David Milliband, who now heads the International Rescue Committee, has been tipped as a possible successor as has French ecology minister Segolene Royal.

Helen Clark's letter reads:

"Dear colleagues,

I am writing to advise all staff that I have informed the Secretary General that I am preparing to leave my position as Administrator at the end of my second term on 19 April.

This will allow the Secretary General to appoint a new Administrator as soon as possible. I stand ready to support the transition to the new leader of the organisation. I have full confidence in our Associate Administrator, Tege Gettu, to act as Administrator if there is a gap between my departure and the arrival of the next Administrator.

This is not my final message to staff - there is much to be done between now and 19 April. There is, for example, a timetable for tabling the draft of the next Strategic Plan to enable it to be discussed at the Executive Board's Annual Meeting on 31 May. It is my desire to see all aspects of the organization in a strong and sustainable state when the next Administrator assumes office.

These are times of change across the UN system. There are post-QCPR reviews being commissioned which may impact on UNDP. While these processes are unfolding, I urge you all to continue to deliver to the high standards for which UNDP is known. Making progress on the SDGs and on supporting national development achievements must continue unabated.

It has been a privilege and an honour for me to lead UNDP for eight years. Our staff are our greatest strength, and I will miss you all. I will offer my thanks and gratitude more fully nearer to my departure."

- NZ Herald