More than one in 10 homes in Scotland would be classed as being in extreme fuel poverty under a planned new law, figures suggest.

A government paper updating fuel poverty estimates that following changes to the Fuel Poverty (Targets, Definition and Strategy) Bill, which is currently making its way through Holyrood, a new definition means the number of  homes in extreme fuel poverty would rise.

Under the legislation, homes where more than 20% of the household’s adjusted net income goes on energy bills are classed as extremely fuel poor.

Civil servants examined Scotland’s extreme fuel poverty rate in 2017 and found the current definition gives a rate of 7.0%, or 174,000 homes, rising to 293,000 (11.9%) under the planned new classification.

However, the rate for general fuel poverty – where 10% of household adjusted net income is spent on energy bills – falls slightly, with the current criteria giving a rate of 24.9% – 613,000 homes -and the proposed definition 23.7% – 583,000 homes.

The Bill proposes a target to cut the number of households affected by fuel poverty to 15% by 2030 and 5% by 2040.

Targets for extreme fuel poverty are 5% for 2030 and 1% for 2040.

Extreme fuel poverty rates were higher for all household types under the new definition compared to the current one, while for general fuel poverty the rate for families rose from 12% to 17%.

In homes for those under 65 with no children, rates rose from around a fifth (21%) to around a quarter (26%) while for older households it dropped from around two fifths (39%) to around a quarter (26%).

Researchers found a “substantial decrease” in fuel poverty rates in rural areas between the current definition (43%) and the new definition (29%), which they said were explained by the introduction of an income threshold under the new definition.

The rate of extreme fuel poverty in rural areas showed little change, going from 16% under the current classification to 19% under the new rules.

In urban areas, fuel poverty rates were slightly higher under the new definition (23%) than the current definition (21%), and extreme fuel poverty rates doubled to 10%.

Housing Minister Kevin Stewart said: “Scotland is one of only a handful of countries to define fuel poverty and our new definition is aligned with income poverty to better reflect those who can’t afford the fuel they need.

“This more accurate reflection of need also takes account of the higher cost of living in remote and island areas, and will aid our aim of eradicating fuel poverty through our robust new targets and achieve a fairer and more socially just Scotland.”

Jamie Stewart, Citizens Advice Scotland energy spokesman, said: “These figures continue to show the scale of the problem which people have been experiencing across the country.

“The Citizens Advice network in Scotland helps hundreds of thousands of people each year, and for thousands of our clients fuel poverty and soaring energy bills is a source of stress and anxiety.

“That’s why we welcomed the Government publishing an energy consumer action plan this week.

“Rising energy prices continues to be a top concern for Scottish consumers and it is important that people are supported on the ground to engage with the energy market in new ways.

“To counter fuel poverty and ever rising energy bills we need a multi-faceted approach from policy makers, government and industry.”