Britain's decision to stall a Franco-Chinese project to build its first nuclear power plant in a generation has fuelled speculation that the new government is reviewing its energy strategy to boost the role of renewables.

Prime Minister Theresa May has given no clear reason for delaying final approval of the Hinkley Point plant, with her spokesman saying only that it was "an extremely important decision that we have to get right".

Critics cite the enormous cost of the 18-billion pounds (21-billion-euro, $23 billion) project as well as security concerns about the involvement of China's major energy group CGN.

They also question whether France's EDF energy giant can deliver on the latest EPR reactors which have been plagued by delays and cost overruns at projects in France and Finland.

Others have asked if a new nuclear plant is the best way to address Britain's energy needs during a time of advances in renewables, particularly wind power, a promising source of energy on an island nation.

Peter Williamson, professor of international management at the University of Cambridge, said the reasons for the delay were "multiple and complicated".

"Not only the questions some people have raised about security but also the question of the economics and the high guaranteed price for the electricity," he told AFP.

EDF would be guaranteed 92.50 pounds per megawatt hour produced by Hinkley Point over 35 years, but that is looking increasingly generous as energy prices fall.

There was also "the question of whether we should opt for a few large nuclear plants or consider new 'mini-nuclear' technologies or other energy alternatives", Williamson said.

- Climate change targets -

The Hinkley Point plant in Somerset, south-west England, is projected to provide seven percent of Britain's electricity needs, filling a gap in capacity while also helping the country meet its climate change targets.

The British government has set itself an ambitious goal of cutting carbon emissions by 57 percent on 1990 levels by 2030.

"The challenge is to deal with the phasing out of coal plants and the decommissioning of old nuclear power stations," said Olivia Gippner, researcher in renewable energy at the London School of Economics.

"I would see this point in time as an opportunity to invest much more heavily in energy efficiency improvements and renewable energy."

In 2015, about 30 percent of Britain's electricity came from burning natural gas, and another 30 percent from coal.

A further 19 percent came from nuclear reactors and 19 percent from renewables such as hydroelectricity, solar and biomass.

But of the eight existing nuclear power stations, only one will still be operational after 2030, while the most polluting coal-fired power plants are due to be closed.

The National Grid, Britain's main transmission company, was obliged to take out contracts with 10 power stations due to be closed to prevent the risk of blackouts this winter.

- Off-shore wind farms -

Hinkley has been on the table for years and EDF was poised to start construction after its board overcame management splits, union opposition and the loss of partner Areva to finally approve the scheme on July 28.

But the new government in London, formed after May took over in the wake of the Brexit vote, said it would be taking another look and make a decision in the autumn.

Experts have now called for the development of less polluting gas-power stations, and for investment in electricity storage that would make wind power more viable.

On Tuesday, the government approved plans by Denmark's Dong Energy to expand a wind farm in the North Sea that, if constructed, would produce almost as much electricity as the two reactors at Hinkley Point.

The company agreed in February to construct Hornsea Project One, which would have a capacity of 1.2 gigawatts by 2020. It has now received planning permission for Hornsea Project Two, which promises up to 1.8 gigawatts.

"The UK's offshore wind industry has grown at an extraordinary rate over the last few years, and is a fundamental part of our plans to build a clean, affordable, secure energy system," said energy minister Greg Clark.