France's long-held support for nuclear energy emerged as a key issue in next year's elections Wednesday as the opposition Socialists and Greens agreed to joint efforts to reduce reliance on atomic power.

The deal marks the first significant move toward limiting nuclear power in France since it embraced atomic energy after the oil shocks of the 1970s and comes amid growing disquiet here after Japan's Fukushima atomic disaster in March.

Green party leader Cecile Duflot hailed the opposition deal as a revolution in French thinking on nuclear energy.

"This was a real break with the past and will, in the case of a victory for the left and environmentalists, mark a change in France's energy policy," Duflot, the national secretary of the Europe Ecologie-Les Verts (EELV) party, said on Canal Plus television.

The French right was quick to react however and warned that reducing atomic power production would threaten France's energy security and cost hundreds of thousands of jobs.

The Socialists and EELV agreed late Tuesday to a deal that will see them jointly campaign in next year's presidential and parliamentary elections to reduce France's reliance on nuclear energy from 75 percent to 50 percent by shutting down 24 nuclear reactors by 2025.

The Socialists would not agree, however, to back the Greens' demand for an immediate end to construction of a new-generation nuclear reactor at Flamanville in western France, which is scheduled to start producing energy in 2016.

France is the world's most nuclear-dependent country, operates 58 reactors and has been a leading international proponent of atomic energy.

But the country's reliance on nuclear energy has been increasingly called into question since the Fukushima disaster, which prompted Germany to announce plans to shut all of its reactors by the end of 2022.

The deal with the Greens is expected to give another boost to Socialist presidential candidate Francois Hollande, who is leading in the opinion polls against incumbent right-wing President Nicolas Sarkozy.

The French right has rounded on Hollande for his nuclear policies and the energy industry has warned of dire consequences if the country moves to abandon atomic power.

"(Hollande) paid too high a price for his deal with the Greens and it is the French people who will foot the bill," Budget Minister Valerie Pecresse said after the opposition deal was announced.

She said the "heavy costs" of abandoning nuclear power would include a 50 percent increase in electricity bills, the loss of "hundreds of thousands" of jobs and increased dependence on foreign energy sources.

Henri Proglio, the CEO of French energy giant EDF, which runs France's nuclear industry, warned earlier this month that "a million jobs will be at risk" if the country abandons nuclear power and "it would cost between 0.5 and 1.0 percent of gross domestic product."

EDF stocks plunged on Paris's benchmark CAC 40 share index after the opposition deal was announced and were down 5.86 percent to 19.52 euros in mid-day trading.

Green party presidential candidate Eva Joly has denounced claims of hundreds of thousands of job losses as "scandalous lies" and said 600,000 jobs would be created by tapping alternative energy sources like solar and wind power.

Sarkozy has insisted he will continue supporting nuclear energy, saying the Fukushima disaster was "not a nuclear accident, it was an enormous tsunami."

"As head of state, I will never reverse course on nuclear" energy, he said last week.

France will vote in the first round of a presidential election in April and potentially a second round in May, followed by parliamentary elections in June.

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