The UK government is gambling with its own climate targets on claims that the Drax power plant will create “negative emissions” because new rules could hand the carbon savings to the US, campaigners say.

The owners of the North Yorkshire power plant have promised ministers that a key project to capture the carbon emissions created from burning biomass wood pellets imported from US forests will count as negative emissions in Britain’s carbon accounts.

However, a working group convened by the UN’s climate authority, the Intergovernmental Panel on Climate Change (IPCC), has begun meetings to draft rules for national greenhouse gas accounting which will apply to “carbon removal” technologies from 2027 at the earliest.

Campaigners at Biofuelwatch, a green group, have warned that there is “a strong argument” that the so-called negative emissions from bioenergy with carbon capture and storage, known as Beccs, should be “attributed to the country where the wood comes from” rather than where it is burned to generate electricity.

Almuth Ernsting, a co-director at Biofuelwatch, said: “We cannot second-guess what the IPCC expert group will decide, but neither can the UK government.”

The government is considering whether to extend a subsidy scheme that pays Drax about £500m a year beyond its 2027 deadline until the end of the decade. The FTSE 250 company, which agreed to pay a £25m fine earlier this year for misreporting its wood pellet sourcing, has already earned more than £7bn in subsidies since work began to convert the former coal power plant to run on biomass in 2012.

Ernsting said: “It is therefore entirely possible that, if the UK government were to grant billions of pounds in new subsidies to help Drax develop Beccs, this would benefit the greenhouse gas accounts of the USA, Canada and other countries exporting pellets to Drax – and not the UK.”

In the past Drax has claimed its biomass generation is “carbon neutral” because the emissions produced from its chimney stacks are offset by the emissions absorbed by the trees grown in North America to produce the pellets.

It has quietly dropped the use of this wording since its own independent advisory board last year cautioned against repeating the claims. The company still insists that it will be a carbon-negative power plant once it fits carbon capture technology to its flues in the 2030s because it is a “widely accepted scientific view”, according to a company spokesperson.

This view has been disputed in recent years by a rising number of scientific studies from European academics. They fear the lag between when the emissions escape from power plant chimneys and when new trees are able to absorb carbon will create a “carbon debt” which could accelerate the climate crisis in the near term.

A Drax spokesperson said the company did not expect the IPCC expert group to amend the rules on Beccs projects because their work would focus on newer carbon capture technologies, such as direct air capture. But in the minutes of the first meeting, seen by the Guardian, there was a presentation on the feasibility of developing new or updated carbon accounting methods for technologies including Beccs.

The Department for Energy Security and Net Zero said: “We follow the agreed international approach for estimating and reporting greenhouse gas emissions under the UN Framework Convention on Climate Change and the Paris Agreement, and we expect the country that captures CO2 to continue to benefit from negative emissions.

“The subsidies for large-scale biomass generators will end in 2027 and we are reviewing evidence on potential support beyond this,” the spokesperson added.