Climate campaigners say they are considering legal action over ongoing coal mining at the UK's largest opencast mine, months after planning permission ran out.

Digging for coal at Ffos-y-Fran, near Merthyr Tydfil, was supposed to stop last September after 15 years.

The mine's operator has applied for an extension and is waiting on a decision.

Merthyr (South Wales) Ltd said it would be "inappropriate to comment at this point".

Daniel Therkelsen, of campaign group Coal Action Network, told BBC News it was "irrational" that neither the local council nor the Welsh government had stepped in to stop the mine from carrying on past the original deadline of 6 September 2022.

He said the mine had in effect granted itself a "de facto" extension for the last eight months, with UK Coal Authority statistics showing that over 100,000 tonnes of coal had been extracted during this time.

Local residents and campaigners had repeatedly contacted the local council with pictures and reports of alleged coal mining, he said.

"If the application for extension that the company has filed is unsuccessful, then that coal isn't going back into the void - it's been sold, it's gone," Mr Therkelsen said.

"We cannot afford that in the midst of a climate crisis and it makes a mockery of the environmental commitments that the current Welsh government has been celebrated for."

The company's request for a nine month extension is set to be discussed by Merthyr Tydfil County Borough Council (MTCBC) planning committee later this month.

The firm recently revised its application, seeking permission to continue mining until 31 March 2024.

After this date "coal production at Ffos-y-Fran would cease completely", according to a letter sent by the council to interested parties.

Plans for a further three years of coaling had previously been floated.

The Welsh government's coal policy prevents the development of new mines or extensions to existing ones apart from "in wholly exceptional circumstances".

Merthyr (South Wales) Ltd argued it qualifies due to its "nationally significant" role in supplying a local source of coal for Tata's Port Talbot steelworks.

But it also acknowledged that there are "insufficient funds" set aside to restore the mine back to green hillside for the local community's benefit as originally agreed, and that it needs time to put a revised plan in place.

MTCBC said that since the submission of a planning application on 1 September 2022 to extend the life of the existing opencast mine, "it has been brought to the council's attention that coal production has continued at Ffos-y-Fran without the benefit of planning permission".

A spokesperson said the determination of the planning application was "the priority for the council".

"Any issues pertinent to enforcement" would be taken in light of the decision taken by its planning committee on 26 April, they added.

The choice facing the council is either to reject the plans or say they are minded to approve them, in which case they would have to refer up to the Welsh government.

A Welsh government spokeswoman said it had issued a direction to the council which prevented it from granting permission unless authorised by Welsh ministers.

On the issue of ongoing mining on site, she said: "Local planning authorities have powers to investigate claims of unauthorised development and are responsible, in the first instance, for considering enforcement action".

Merthyr (South Wales) Ltd said that having "received confirmation that solicitors are involved for the campaigners and proceedings are being contemplated" that it would be "inappropriate to comment at this point".

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