The survey of 2,000 people, by Populus on behalf of Greenpeace, showed a quarter are in favour of Hinkley, while 44 per cent oppose it. Previous polls this April and in October 2015 put support at 33 per cent and 29 per cent respectively.
It comes as the government prepares to make a final decision on Hinkley later this month, after it was unexpectedly delayed by Prime Minister Theresa May earlier this year.
Hinkley is expected to provide seven per cent of the UK's electricity over its estimated lifetime of 60 years, however the project has been dogged by concerns over safety, security and the high costs involved. It's due to start generating power in 2025, although experts have warned it is unlikely to meet this date.
The poll also showed just under two thirds said they believed the government should prioritise an energy system based around renewables, while 16 per cent believed it should prioritise nuclear and five per cent wanted policymakers to focus on gas-fired power stations.
John Sauven, executive director at Greenpeace, said: "The public knows what the government has yet to learn — investment in renewables should be prioritised over nuclear power. The government shouldn’t risk taxpayers' money on old fashioned, flawed technology. It should be investing in the future.
“Advances in renewable energy like offshore wind, alongside battery storage, energy efficiency innovations and wires that carry electricity under the sea connecting us to other countries are the future for keeping the lights on.