Image caption Ohi's reactor 4, Japan's last functioning reactor, went offline in September

Japan is to significantly slash its greenhouse gas reduction target in the wake of the Fukushima nuclear disaster.

It will now aim to achieve a 2020 target of 3.8% below 2005 levels.

This replaces a previous commitment to reduce emissions by 25% from 1990 levels.

The moves come with all of Japan's nuclear power plants currently offline - forcing the country to increase its burning of fossil fuels.

The move was announced in Tokyo by Chief Cabinet Secretary Yoshihide Suga. The new target represents a 3% rise over 1990s emissions levels, a comprehensive turnaround from the 25% reduction target.

But Mr Suga said the previous target - set under a government led by the now-opposition Democratic Party - had been "totally unfounded".

"Our government has been saying... that the 25% reduction target was totally unfounded and wasn't feasible," he said.

'Less ambition'

Speaking at UN climate change talks in Warsaw, Japan's chief negotiator said the move was based on new circumstances.

"The new target is based on zero nuclear power in the future. We have to lower our ambition level," said Hiroshi Minami.

Acknowledging the move would attract criticism, he said the target could be adjusted if the nuclear situation changed.

Prior to the 2011 earthquake and tsunami, Japan generated more than a quarter of its power from nuclear energy.

But since the disaster, its 50 reactors have been mostly idled for safety checks or scheduled maintenance, amid a public backlash against nuclear energy.

Japan's last operating nuclear reactor, at Ohi, was turned off in September and analysts say the country will be without nuclear power until December at the earliest.

So far, power companies have applied to restart about a dozen of the reactors but this will take time because of safety checks and legal hurdles.

Prime Minister Shinzo Abe wants to see the reactors back on line, as they are a vital part of his plan to turn the economy around.

Since the Fukushima disaster, Japan has been forced to import huge amounts of coal, liquid natural gas and other fuels.