South Korea's top opposition leader vowed Monday to gradually reduce the country's reliance on nuclear energy if her party gains a majority in next month's general election.

South Korea relies on 20 nuclear reactors to meet about 35 percent of its power needs. The government has vowed to stick to the programme despite heightened concern following Japan's nuclear disaster last year.

"I want to see the Fukushima crisis as the last shocking warning for mankind about problems with nuclear power plants," Han Myeong-Sook, chairwoman of the main opposition Democratic United Party, told a panel debate with journalists.

Fears over nuclear power grew worldwide after Japan's earthquake and tsunami on March 11, 2011, badly damaged the Fukushima nuclear plant.

On Sunday anti-nuclear protests were held in Japan and other countries to mark the first anniversary of the disaster.

The disaster ignited debate in South Korea on the use of nuclear power in what is Asia's fourth largest economy and has become a political topic before the parliamentary election on April 11.

Han said her party would stop plans to build more nuclear plants and gradually close down old facilities.

"The party will push to invest in renewable, alternative energy" which is safe and creates more jobs, she said.

The conservative New Frontier Party has a comfortable majority in parliament. But surveys show support is waning due to social and income inequality as well as an economic slowdown.