Low-carbon power generation in the UK increased by just 1 terawatt hour (TWh), or less than 1 per cent of current capacity in 2019 - the slowest growth in a decade, according to sector-tracking website Carbon Brief.

In an analysis, Carbon Brief said that growth will need to double in the 2020s to meet UK climate targets while replacing old nuclear plants as they retire.

The UK’s electricity makeup has changed considerably in the last decade. Low-carbon sources make up around 54 per cent of generation with just 43 per cent coming from fossil fuels. Of the latter, 41 per cent is from gas and just 2 per cent from coal. This compares to 75 per cent fossil fuel generation in 2010.

While power from renewables grew by nearly a tenth in 2019, this was offset by falling nuclear generation due to ongoing outages at Hunterston and Dungeness reactors.

The 2020s will see seven of the UK’s nuclear plants decommissioned - assuming their lifespans are not extended - with Hinkley Point C the only new plant scheduled to replace them at spiralling cost.

To meet goals to clean up energy generation as part of targets to tackle climate change, Carbon Brief said the UK requires a “rapid step up in the pace of low-carbon expansion”.

On average, the UK has seen around 9TWh of low-carbon generation added to the grid in the last decade, with just 1TWh coming last year. Carbon Brief says that to meet goals, the UK will need to see increases of at least 15TWh each year in combination with electrification of transport and heating.

Hinkley Point C will help with this goal somewhat by generating around 25TWh for the grid once the facility is completed (current ETA: 2026), although this will only compensate for approximately half of the power generated at present by the nuclear plants set to be decommissioned. Meanwhile, the Hornsea One scheme - dubbed the world’s largest offshore windfarm - will generate around 5TWh each year.

Carbon Brief warned that it was not certain the offshore wind farms could clean up the grid enough to meet the 2030 goal without increases from other sources such as onshore wind, solar and additional new nuclear.

A separate National Grid analysis for 2019 has revealed that Britain’s grid saw a milestone in which electricity supplies from zero-carbon tech - wind, solar, hydro and nuclear - outstripped fossil fuels for the first time for the year.

Luke Clark, from industry body RenewableUK, said energy policy had to support a full range of clean power sources to reach the new legal target to cut emissions to net zero by 2050.

“Offshore wind will be the backbone of Britain’s future clean energy system, with 40 gigawatts installed by 2030,” he said. “But to meet our targets we need to double down on all of our renewable resources by unblocking onshore wind and maximising the potential of innovative technologies like floating wind and tidal power.”

Energy UK’s interim chief executive Audrey Gallacher said: “While these figures show just how much progress the energy sector has made in moving to cleaner sources of power and reducing emissions over the past few years, they are also a stark reminder of how much further and faster we have to go with the net-zero target in place.”

A Business and Energy Department spokesman said: “We have cut our emissions by over 40 per cent since 1990, but plan to go further, faster, backed up by an average of £9bn of investment in renewables annually as we aim to eliminate our contribution to climate change.”