UK voters' concerns over the country's exit from the EU have "risen strongly" over the past month as Brexit divorce talks loom, a poll from Ipsos MORI showed on Wednesday (15 February).
The survey, of more than 900 people between 13 and 26 January, showed that Brexit/EU climbed from 36% to 41%.
Brexit also leads when the public are asked to name the single biggest issue facing the UK, with 27% of respondents citing the split from the EU over NHS/hospitals at 17%.
But this month's poll, commissioned by The Economist magazine, found that almost half (49%) of UK voters considered healthcare to be one of the biggest issues facing the country.
"The proportion who name the NHS as one of the biggest issues facing Britain is high amongst nearly all demographic groups, with particular spikes amongst women (53%), those aged over 65 (55%) and suburban-dwellers (54%)," said Gideon Skinner, head of political research at Ipsos MORI.
"It is the biggest issue across all social grade and age groupings, with the exception of those aged 55+ and from social grades ABC1. Amongst this group it is joint-top with Brexit."
However, one issue which has fallen in the concerns index is immigration, down from 36% to 31% as one of the most important issues for the British public and a fall from 19% to 13% as the top issue for UK voters.
The UK government plans to curb immigration as part of its split from the EU, with Prime Minister Theresa May planning not to maintain Britain's membership of the EU's single-market, which requires nations to sign up to free movement of people rules.
But the Conservatives have consistently failed to meet their "tens of thousands" net migration pledge.
The latest Office for National Statistics (ONS) estimates show that net migration hit more than 335,000 in the year to June 2016.
The issue was a major theme of the EU referendum, with the Vote Leave campaign endorsing an Australian-style visa system. May, meanwhile, has promised to trigger Brexit talks by the end of March.