Japan is drastically scaling back its target for reducing greenhouse gas emissions.

The new target for 2020 – 3.8% below 2005 levels – comes after the Fukushima nuclear disaster forced the country to turn to fossil fuels. It replaces the nation’s initial ambitious goal to slash emissions by 25% from 1990 levels.

Considered to be the fifth largest source of greenhouse gas emissions, Japan’s decision to back away from its previous target could set back UN talks to tackle climate change.

Yoshihide Suga, Japan’s Chief Cabinet Secretary is said to have told reporters the previous target was “unrealistic”. He said: “Our government has been saying … the 25% reduction target was totally unfounded and wasn’t feasible.”

The UK Government said the news is “deeply disappointing”.

Energy Secretary Ed Davey believes Japan can be persuaded “to change her mind again to resume her leadership role in the world on climate change”.

He said: “This announcement runs counter to the broader political commitment to tackle climate change, recently reaffirmed by G8, as well as the enhanced ambition we have seen from the world’s major emitters.

“We urge the Government of Japan to reassess this decision and increase the target in the near future as it clarifies its future energy policy.”

Japan has however reaffirmed its long term emissions reduction target of 80% by 2050.