The French nuclear industry is in its “worst situation ever” because of a spate of plant closures in France and the complexities it faces with the UK’s Hinkley Point C power station, according to a former Électricité de France director.

Gérard Magnin, who called Hinkley “very risky” when he resigned as a board member over the project in July, told the Guardian that the situation for the state-owned EDF had deteriorated since he stepped down, with more than a dozen French reactors closed over safety checks and routine maintenance.

The closures have seen Britain this week exporting electricity to France for the first time in four years. An industry report on Tuesday also warned that the offline reactors could lead to a “tense situation” for energy supply in France, in the event of a cold snap this winter.

Instead of backing new nuclear, the UK and France should capitalise on falling wind and solar power costs and help individuals and communities to build and run their own renewable energy projects, said Magnin. He founded an association of cities switching to green energy, joined the EDF board in 2014, and is now director of a renewable energy co-op in France.

“The most surprising [thing] for me is the attitude of the UK government which accepts the higher cost of electricity … in a time where the costs of renewables is decreasing dramatically,” he said. “In 10 years [when Hinkley Point C is due to be completed], the cost of renewables will have fallen again a lot.”

Of the Hinkley C design, known as the European Pressurised Reactor (EPR), Magnin said: “A lot of people in EDF have known for a long time the EPR has no future – too sophisticated, too expensive – but they assume their commitments and try to save the face of France.”

The UK’s business department conceded in September that by the time Hinkley is operational the price of electricity guaranteed to EDF will be above the comparable costs for large scale solar and onshore windfarms. Officials argued that using renewables instead would cost more in grid upgrades and balancing the intermittent nature of wind and solar.

But in a comment article for the Guardian, Magnin said renewables would still be able to match new nuclear. “Renewable energies are becoming competitive with fossil fuels and new nuclear, such as Hinkley Point, where EDF will try to build the most expensive reactors in the world and provide electricity at an unprecedented cost,” he wrote.

A spokesman for EDF said the company was confident its reactors in France would restart soon after tests were complete.

He added: “EDF has full confidence in the EPR design which is why we and our Chinese partners CGN have invested £18bn in our project at Hinkley Point C. Final testing is underway for our EPR unit in Taishan in China which is due to be operational next year. As our chairman Jean-Bernard Lévy said recently, the EPR is a technology of the future, combining performance, safety and predictability.”

On Wednesday the European commission is due to publish plans on how it will support an increasing amount of renewable energy on Europe’s grids, and how it will meet its climate change commitments under the Paris Agreement. Around seven or eight draft pieces of legislation are expected in the “winter package”, plus funding for cleaner energy, but green groups fear renewables will lose the priority they get on electricity grids.

Magnin said that the EU’s climate targets are used in France as a way to maintain a status quo which sees nuclear – a low-carbon power source – provide around three quarters of the country’s electricity. “Climate change issues are used as arguments to maintain the current system,” he said.

Wind and solar provide less than 4% of France’s electricity, but Magnin said the European commission and governments should support community-owned green energy projects to grow that share. Such an approach would overcome opposition to renewable power sources, and secure funding, he said.

Separately on Tuesday, the trade association for national grids across Europe issued a warning that France was faced with its lowest supply of power from nuclear in a decade because of plants being taken offline for safety checks.

The European Network of Transmission System Operators for Electricity said that further reactors would be taken offline, potentially leaving France dependent on imports in December and February, depending on how cold the weather is. But it said that Europe as a whole had sufficient power plants to cope with normal and severe conditions over the winter.

“Identifying the problems facing France and the UK this winter only goes to highlight the importance of investing in new capacity. Events across the Channel have shown that relying on old capacity is risky, with France’s nuclear plants proving as unreliable as our coal-fired ones,” said Dr Jonathan Marshall, energy analyst at the Energy and Climate Intelligence Unit, a UK-based thinktank.