Household bills could rise if the government further delays its plan to rid the power network of polluting fossil fuels by 2035, the National Audit Office (NAO) has warned.

Energy officials committed to the target almost 18 months ago, but their plan to deliver it was delayed by the energy crisis as they focussed instead on tackling soaring bills, the auditors said.

However today they warned it was not clear when the new energy and net zero department would come up with a plan to decarbonise the grid, which could drive up household bills even further.

"The longer it takes before government finalises its delivery plan, the greater the risk that it won't achieve that ambition to decarbonize power by 2035, or that doing so will cost consumers more," warned Simon Bittlestone, NAO's director of value for money studies.

"Decarbonizing power is really the backbone of achieving net zero, as we're all likely to switch to electric vehicles and potentially use electricity to heat our homes, but it will require a step change investment and modernisation," he told Sky News.

Generating electricity accounts for 13% of emissions in the UK. Some 40% of electricity is generated by fossil gas.

Although the country has so far decarbonised faster than any other G7 country, according to government data, demand for electricity is set to soar 60% by 2035 as the economy continues to shift away fossil fuels.

Meeting that demand requires an enormous surge in renewable wind and solar power, including by building three times as much offshore wind capacity in eight years as in the last two decades.

The government should prioritise lifting an effective ban on onshore wind, urged Stuart Dossett, senior policy adviser at think tank Green Alliance.

"Onshore wind is one of the quickest to build and cheapest forms of electricity we have," he told Sky News.

The shortfall in the UK is "slowing us down from moving as quickly as we need to move to cut carbon emissions and to bring energy bills down," added Mr Dossett. "Renewables are significantly cheaper than gas, and gas is what is driving up the price of energy".

Recent UK prime ministers have changed their minds on onshore wind, and Rishi Sunak's administration is currently running a consultation on relaxing rules.

Costs to consumers

The report detailed how Britain's outdated grid is already costing taxpayers, and will only increase without a plan.

That's because when power generated from a plant exceeds demand, or what the grid can accommodate, energy companies have to limit their output, which costs money that is paid by the consumer.

The grid also needs upgrading and expansion so it can transmit power from where it is made, for example in Scotland, to where it is needed, potentially in Cornwall.

The auditors warned the government must make up its mind which technologies will be used to power the UK during cloudy and calm days, including batteries for short-term power, longer duration energy storage like compressed air, hydrogen from renewables and nuclear.

A Department for Energy Security and Net Zero spokesperson said since the energy crisis set in last year "our focus has been on delivering essential cost of living support, including paying half a typical household's energy bills this winter, because this is the primary focus for families across the country".

"We have launched world-leading blueprints, such as our British Energy Security and Net Zero Strategies, with many plans already implemented to ensure we are on track to achieve our 2050 net zero target," they said.

"Our targets are ambitious, however, we haven't taken our foot off the pedal and our commitment to decarbonise the UK's electricity system by 2035 remains resolute."