Helen Clark is thought to be considering whether to withdraw from the contest to become the next UN Secretary General after a disappointing result in a second informal ballot.

The former Prime Minister slipped from sixth place to seventh place out of 11 candidates.

Clark hinted in a tweet she would be reconsidering her candidacy: "Disappointed by outcome. Will discuss over coming days."

Foreign Minister Murray McCully said any decision was entirely over to Clark.

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It was clear from the increase in "discourage" votes for almost every candidate, that once a country had decided on a first preference, they had tried to discourage others to advantage their first preference.

Clark had not been the first preference of enough countries to date.

"It doesn't mean that she wouldn't emerge from the discussions that will occur much later on as a very viable compromise candidate - which was always the only way she could come through this," McCully told the Herald on Sunday.

"But the numbers are unflattering."

Former Portuguese Prime Minister Antonio Guterres remains well ahead in the informal ballot count.

Clark's "encourage" votes slipped from 8 to 6, her "discourage" votes increased from 5 to 8, and "no opinion" votes have gone from 2 to 1, according to figures leaked to Foreign Policy magazine.

When asked if the Maori Party's public criticism of Clark in the past week may have had any bearing on the results, McCully said "none whatsoever".

"What we have got here is a very strong series of tactical plays where, once you've decided who you want, you try and finish off the others and Helen Clark hasn't been No1 for enough countries around the council table in the polls to date."