More Leave voters defected to Remain than vice versa, driven by concerns about risk and uncertainty, as well as arguments around the economy.
Pollster TNS' analysis added few of those that intended to vote Remain switched to Leave. Of those who did, immigration and having a strong British identity were the main drivers.
Its results were based on qualitative research with an election day voter panel of 200 voters, featuring people who intended to vote in the election.
Many of the voters TNS surveyed switched or made up their mind in the final days of the EU referendum campaign.
It added that one in six moved from a previously undecided position to supporting Remain or Leave, with the group being fairly equally split between the two rival camps.
The undecideds who moved to Remain cited fear over the impact of Brexit on the economy, as well as the uncertainty and risk attached to a future outside of the EU.
“I just think that you can't really tell what the future holds if we leave the EU but if we stay I think right now we're good as an economy …," one respondent said.
Those who moved to Leave were swayed by major campaign issues of both immigration and the NHS.
“Purely because I think the money we spend on being a member of the EU, could be better spent on the NHS, and schools, and public services," another respondent said.
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