TEPCO said Monday the Japanese government will control up to three-quarters of the voting rights at the embattled nuclear plant operator after a massive injection of public funds.

Tokyo Electric Power said it would issue preferred shares worth 1.0 trillion yen ($12.6 billion) to the state-run Nuclear Damage Liability Facilitation Fund under a previously announced bailout programme, effectively nationalising one of the world's largest utilities.

The agency is slated to buy preferred shares giving it at least a majority of voting rights at the operator of the crippled Fukushima Daiichi plant, with an option to raise that figure to 75.84 percent.

Earlier, TEPCO said the government would own a majority share of the firm, with more than 50 percent of voting rights and possibly as much as two-thirds.

TEPCO is facing massive clean-up and compensation costs after last year's quake-sparked tsunami swamped reactors at Fukushima, sending them into meltdown.

The government will complete its share purchase by July 25, TEPCO said.

Last week, the utility posted a massive 781 billion yen net loss in the fiscal year to March on disaster-related costs, as well as increased imports of fossil fuels to make up for a nuclear power shortfall.

The government said this month it would inject one trillion yen into the embattled company as part of a 10-year restructuring plan aimed at preventing it from going bankrupt.

Decommissioning Fukushima's reactors and cleaning up the surrounding area, about 220 kilometres (140 miles) northeast of Tokyo, is expected to take decades, while TEPCO also faces ballooning compensation claims.

As the sole provider of electricity to Tokyo and a vast surrounding region in eastern Japan, the company is responsible for maintaining a stable power supply to its millions of customers.