The government has announced a fresh feasibility study into the Severn Barrage, a tidal power plan that could provide about 5% of UK electricity.
John Hutton said the Severn Barrage concept was "visionary"
Speaking at the Labour Party's annual conference in Bournemouth, business and enterprise secretary John Hutton said the concept was "truly visionary".
Some environmental groups have warned the barrage could affect wildlife.
The idea was first floated about 150 years ago, but environmental and cost concerns have always blocked approval.
It was last seriously considered in the 1970s and 80s.
Last year's governmental energy review opened the door again, saying that the barrage should be re-evaluated.
HOW TIDAL POWER WORKS
As tide comes in, sea water passes through barrage to landward side
At high tide, sluice gates shut, trapping water in estuary or basin
When tide recedes on sea-side of barrage, sluice gates open
Water flows through barrage, driving turbines and generating power
Power can be generated in both directions, but this can affect efficiency and economics of project
Now Mr Hutton has signalled that a multi-million pound feasibility study will go ahead, citing climate concerns as the main driver.
"The government Gordon Brown leads will not be among those who say they want to tackle global warming by moving to low-carbon energy sources, but then oppose every opportunity to do so," he told conference delegates.
The study will examine the social, economic and environmental aspects of the barrage.
It could extend from the South Wales coast near Cardiff across the estuary to Weston-super-Mare.
Against the tide
Reaction to the announcement from conservation groups has not been positive.
The Royal Society for the Protection of Birds (RSPB) said the barrage would put thousands of birds, salmon and other fish at risk.
The estuary contains mudflats, saltmarshes, rocky islands and food that support some 65,000 birds in winter.
"The Severn estuary is one of the UK's most important sites for water birds," said the RSPB's conservation director Mark Avery.
The barrage would be 16km (10 miles) long
It would power more than 200 turbines
Planners say it could create 35,000 construction jobs and between 10,000 and 40,000 permanent jobs
The barrage could be generating electricity within 11 years, say planners
"A barrage would do enormous damage. There could be much better ways of harnessing the Severn's power, and the feasibility study should examine tidal lagoon and tidal stream schemes which could do less damage and generate more energy."
Tidal lagoons are artificially created offshore pools.
Water would flow through turbines in and out of the lagoons as the tide rose and fell. Some analysts say this could generate more power than the barrage with less local environmental disruption.
With the barrage carrying an estimated £14bn price-tag, some believe the lagoon concept would also be cheaper.
However, it could not provide the potential economic side-benefit of a new connection between Wales and southwest England.