He said it would be interesting to see if the parties would raise the issue again ahead of next month's election.
Last election Labour campaigned on raising the retirement age to 67 and this was cited as one reason it didn't do so well at the polls. But this time Labour has said it wouldn't raise the age of eligibility if elected.
Tennent-Brown said National's proposal had raised a lot of comment when announced but that had died down. He said one of the challenges with National's plan was that the change wouldn't happen until a long way down the track.
"Things like housing affordability, which is a problem in the here and now, are probably going to be one of the things that are front of mind."
But the other side was that the policy would be implemented if National was re-elected, he said.
The research also found older New Zealanders were more likely to oppose raising the retirement age despite not being affected by the change.
Of those surveyed, 27 per cent of people aged 50-59 strongly disagreed with the proposed change, and only 9 per cent agreed with it. For those under 39, 16 per cent strongly disagreed and 7 per cent strongly agreed.
Tennent-Brown said it was surprising that the strongest opposition came from older age-groups who would not be affected by the change.
But it might be because older voters didn't like policy being tinkered with. They had already seen the age of eligibility change over their lifetime when the age was temporarily dropped to 60 and then increased again.
"People don't like uncertainty."
Tennent-Brown said for younger people the change might seem a long way down the track, especially if their immediate concerns were getting a career and buying a house.
The survey was based on 773 online interviews with adults aged 18 and older across New Zealand during the second quarter of 2017.
Strong views
• 20% strongly oppose lifting the retirement age
• 11% strongly agree with it