Labour unveiled a multi-billion dollar plan to give every New Zealander three years of free tertiary education in January. It also revealed some of its high-level Future of Work Commission findings.
Labour leader Andrew Little said the result was "obviously disappointing" and reflected a "bad couple of weeks" in March.
"I think it's a question of us knuckling down, understanding the need for a clarity of message, and sticking to the things that are important to New Zealanders," he told the Herald.
In late March, Mr Little was mocked in Parliament after appearing to lay the blame for a migrant boom on ethnic chefs. Labour's consideration of a universal basic income in New Zealand was also questioned because of its potential cost.
Mr Little and most of his caucus opposed a change of flag in the referendum last month, and the party made a strong stand against New Zealand signing the TPP - a stance which caused some pro-free trade MPs to break ranks.
The Labour leader fell slightly in the preferred Prime Minister poll, dropping 2 points - within the margin of error - to 7 per cent.
That meant he was overtaken by New Zealand First leader Winston Peters, who moved up 1 point to 10 per cent.
National's positive result came despite Mr Key's public advocacy for a change to a silver fern flag, which was soundly defeated in a referendum last month.
Mr Key's preferred Prime Minister ranking was barely moved, falling 1 point to 39 per cent.
This year, the Government has been promoting the Trans Pacific Partnership deal around the country in a series of roadshows.
The April 6 cut-off date for the poll meant it was unlikely to have taken into account any possible fallout from the Panama Papers scandal, which shone a light on New Zealand's tax-free foreign trusts.
Despite leading a strong campaign against a flag change, New Zealand First's support was nearly unmoved, falling 1 point to 9 per cent.
The Green Party, which announced a policy to make Kiwibank more competitive, rose 2 points to 10 per cent.
