On July 17, a TVNZ Colmar Brunton poll put support for Labour at 27 percent -- down 7 percentage points from its previous poll in May -- while National was up one point on 53 percent. The result was the lowest for Labour in the poll in a decade.
Just a week before, a TV3 Reid Research poll had National at 55.1 percent and Labour at 29.9.
Mr Goff spoke to Rotary members at a breakfast in Napier this morning, outlining Labour's economic policy.
He told Hawke's Bay Today afterwards the poll didn't reflect support he'd found around the country, particularly for the capital gains proposal.
"When people understand it they are changing their vote and they're changing it in our direction," he said.
An election based on today's poll result would see Napier-based Labour MP Stuart Nash lose his list seat in parliament, but Mr Goff said that was not a concern.
"We're not intending to get a result like that," he said.
Mr Nash, who is also the party's revenue spokesman, would "absolutely" retain his seat, and also had a chance of winning his Napier seat from National MP Chris Tremain, he said.
"I know he's got a big majority to pull up but I wouldn't rule him out to be able to win the electorate off National."
The poll was conducted while Prime Minister John Key was receiving positive coverage over his United States trip, during which he met President Barack Obama.
Mr Key recorded 53 percent support as preferred prime minister, compared to Labour leader Phil Goff's 6 percent.
The poll was conducted between July 21 and 25, and surveyed 1004 eligible voters. It has a margin of error of 3.1 percentage points.