Overall National polled 51 per cent, marginally up on party support in December from 50.4.
Its support among women, 45.4 per cent, is the same as it was in December.
Mr Key's popularity as preferred Prime Minister is down marginally to 64.6 from 65 per cent in December, which was the first full poll after the September general election.
Andrew Little, who took over the Labour leadership in November is on 13.9 per cent, virtually unchanged from 13.6 in December.
And New Zealand First leader Winston Peters has bounced up to 12 per cent on the back of his win in the Northland byelection a month ago.
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Mr Little, who is in London, said last night while the movement for Labour had been "pretty negligible" it was the sort of result that was expected at the start of a parliamentary cycle.
"I'm not fazed or for that matter boosted by it," Mr Little said.
Last week, as the ponytail story went global, Mr Key also featured prominently in the build-up to Anzac Day, including hosting Australian Prime Minister Tony Abbott for a dedication ceremony at Pukeahu, the war memorial in Wellington.
Since the December poll, National has repeatedly talked down the chances of achieving its main election promise of getting the books back into surplus in the current financial year.
New Zealand First's support outside of Auckland has increased a little since December, from 5.8 per cent to 7.2, and the Greens appear to have increased support in Auckland from 11.3 per cent to 15.8 per cent - although the 3.6 per cent margin of error for party vote figures does not apply to smaller breakdowns.
• The poll of 750 eligible voters was taken between April 17 to 26. The party votes are of decided voters only. Undecideds were 11.8 per cent. The results have a margin of error of plus or minus 3.6 per cent.
