The coal extracted from the planned Cumbrian mine may go further overseas, rather than be used in Britain and the EU as the company has claimed, the public inquiry into the scheme heard on its opening day.

West Cumbria Mining’s (WCM) proposals to extract 2.7m tonnes of metallurgical coal a year from a site off the Cumbrian coast at St Bees are being examined by the Planning Inspectorate.

WCM has said its “indigenous” coal would principally supply British steelmaking and industry in EU countries, while creating hundreds of well-paid jobs for people in west Cumbria. According to current levels of domestic demand for coking coal, about 15% of the coal extracted underneath the Irish Sea would go to UK-based companies, with WCM having proposed to export the remainder to Europe.

But opponents to the project have pointed to a document submitted by WCM to the inquiry, arguing it showed that much of the coal exports the mine would produce could travel well beyond the EU markets WCM had suggested it would supply.

“The reality is the vast majority of WCM’s coal is destined to go abroad,” said Estelle Dehon, the legal representative acting on behalf of the South Lakes Action on Climate Change group (SLACC). “WCM’s coal is likely to go to Europe, [but is] not exclusive to the EU – including Turkey, Bosnia and Herzegovina, and Serbia.”

She added that markets in Japan and India had also been mooted.

The document suggests Turkey may be the largest market for WCM’s coking coal. Turkey is the only member of the G20 that is yet to ratify the international commitments enshrined in the 2015 Paris climate agreement.

Dehon also cast doubt on WCM’s promise of jobs, saying no methodology had been provided by WCM to support job creation claims or associated apprenticeships, despite SLACC having requested the information for a number of months. And concerns were raised about the impacts on the “ancient woodland site” at nearby Roska Park and Bellhouse Gill Wood, where pipe-jacking work is planned to take place.

The communities secretary, Robert Jenrick, called the public inquiry in early March, amid rising pressure over the UK’s climate commitments – in view of its role as Cop26 host this November – that forced him to reconsider his initial decision to wave through the plans.

The inquiry is expected to last about four weeks and will hear the respective cases of all sides – including Cumbria county council and Friends of the Earth – after which the planning inspector will publish his recommendations and then the final decision will rest with the secretary of state.

Earlier on Tuesday a local Tory MP who had previously backed the mine announced he had changed his mind. Dr Neil Hudson, the MP for Penrith and the Border, said: “On reflection I now believe that the project should not go ahead. The world is changing and we are witnessing ever-increasing adverse weather events leading to catastrophic floods and fires.

“I ask that the government now acts to cancel this project and have made representations to that effect to government and the public inquiry.”

The Tory MP Trudy Harrison, in whose Copeland constituency the deep mine would be constructed, told the inquiry that the opposition to the project was simply “gesture politics”.

Meanwhile, Lee Anderson, a former miner who is the Conservative MP for Ashfield in Nottinghamshire, argued the scheme was a crucial opportunity to revitalise domestic industry. He said: “We’re on track to move away from coal in steelmaking by 2049. And that should always be our target. But we have the chance, in the meantime, to use British coal and not foreign coal.”

WCM was contacted for comment.