The Scottish Government faces a potential shortfall of more than £6 billion on a pledge to make homes more efficient and cut fuel poverty.

WWF Scotland revealed the figure in a report which called for a review of the legally binding emissions targets set by the SNP.

The Scottish Government has targets to cut greenhouse gas emissions by 42% by 2020 relative to 1990 levels, and a commitment to end fuel poverty by 2016. Housing is behind one-quarter of emissions and one-third of energy demand, and is a major contributor to fuel poverty, which means improving energy efficiency is vital to both targets.

The Government's emissions reduction target for housing is 36%, which it said would require £4.6bn investment.

WWF says the Government should aim for the sector to achieve its full share of the 42% cut because "technology is readily available, warm homes are popular, it helps deliver on fuel poverty and green jobs". But achieving this would cost £7.7bn, while the funding available is £1.5bn.

Elizabeth Leighton, of WWF Scotland, said: "Without a dramatic increase in investment to make our homes more energy efficient, Scotland's climate and fuel poverty targets are at risk."

A Scottish Government spokesman said: "Over this spending review period, we are spending around a quarter of a billion pounds on fuel poverty and energy efficiency."