Don Brash, former leader of both ACT and National, says Labour will take out the 2017 election.
"It looks as if they might [win]. Momentum is certainly on Labour's side and National is vulnerable in certain areas," he told The AM show on Friday morning.
It comes after a Colmar-Brunton poll released on Thursday evening saw Labour ahead of National for the first time since 2007.
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He said National is vulnerable in a range of areas including the economy - but he worries Labour doesn't have the answers either when it comes to lifting the per capita growth rate.
"They're [National] vulnerable on the economy, they'll say 'no we're not, the economy's growing strongly' but per capita income is barely moving at all," Dr Brash said.
He also said National is vulnerable when it comes to house prices, but he believes Labour needs to be more specific about how much the price of a house should be - saying they are "terrified" to name figures.
Dr Brash said 'the Ardern effect' is bringing Labour up in the polls but he wonders how much of the party's surge is down to having a new face at the helm.
"She's shiny, she's new, and I think that will count for a lot. In 12 months time if the election was held then, it wouldn't be anything like so clear."