Seymour had risen to 7.7 per cent - and NZ First leader Winston Peters was up 1.9 points to 4.2 per cent.
The poll continues to show a slide in Luxon's personal polling. This is often seen as a leading indicator of the party vote.
Luxon's net personal favourability is -1 per cent, down from 1.2 per cent in July. It is well off the +15 per cent he scored in December, after he took over the party leadership.
Ardern's net favourability is +9 per cent, down from 13.8 per cent last month - a greater fall than Luxon's. In the last year, her polling peaked in September 2021 when her net favourability was 31.7 per cent.
Seymour's net favourability was -7 per cent. He has been climbing since last September when he polled -17.1 per cent.
The most positive trend for National is that New Zealanders continue to feel the country is on the wrong track. A net 13 per cent of people polled feel the country is on the wrong track. This shows a continuation in the trend since February of this year, the last month more people thought the country was on the right track than the wrong track.
Men and women appear to have similar views on the political scene.
Amongst women, 46 per cent support parties of the centre right and 45 per cent support the centre left.
Among men, 45 per cent support the centre-left and 43 per cent support the centre right.
The timing of the poll will give National cause for optimism. It takes in some of the party's recent scandal, but excludes Labour's.
But any optimism should be couched in caution, as the polling period also included a period where National should have been dominant: its conference.
The poll was taken from August 3 to 11, including the weekend of National's annual conference.
The last three days overlapped with the news about National's Tauranga MP Sam Uffindell's involvement in bullying at King's College from his school years. Uffindell was stood down while an investigation into subsequent claims about his behaviour at Otago University is done by Maria Dew QC.
It was taken before Hamilton West MP Gaurav Sharma's public claims that he was bullied by the party whips over staffing issues in his office - public statements that resulted in his suspension from the Labour caucus on Tuesday.
National was on 34 (down 3), Labour on 35.2 (up 0.5), the Green Party on 9.5 (up 1), Act on 11 (up 1), Te Pāti Māori on 3.5 (down 0.2) and NZ First on 2.6 (down 0.7).