Residents say they have been "let down" by their local council after a massive battery energy storage site was approved on appeal by Welsh government planning inspectors.

Developers Innova have won a case to build a 400MW facility on a site near the village of Rhostyllen, Wrexham, which it said could power 900,000 homes.

Campaigners claim Wrexham council officers failed to represent them properly at the inspectorate hearing.

But the authority said it had presented as robust a case as it could and would now have to pay legal costs.

Battery energy storage sites (BESS) are seen as an important part of reducing use of carbon by storing energy from renewables and releasing it to the grid when needed.

Campaigners are concerned about the development's effects on agricultural land, biodiversity, the area's character and fire safety.

"We were told by Wrexham planning department that they would represent us vocally and with evidence," said Alan Jones, chairman of Esclusham Community Group which has campaigned against the development.

"We feel they didn't represent us at all.

"Because we weren't represented, we have no case to take this to appeal so we're really disappointed."

Developers appealed to inspectors at Planning and Environment Decisions Wales after Wrexham council failed to consider the application in the required time.

The council's own planning committee then decided the local authority should oppose the plans at a hearing in July.

Mark Andrew, from the local community council, said it had "hoped the local planning department would put a good argument in place".

"The inspector said that no evidence was given against the case for the battery farm," he said.

"It's angered so many people."

Wrexham council said a senior officer was at the hearing and the authority had "presented as robust a case as it could explaining the reasons for the planning committee's decision".

"The disappointment of the local community about the outcome of the appeal is understandable," it said.

The council said it was now awaiting an invoice from the developers for costs after the inspector "concluded the council had acted unreasonably".

Innova said it was pleased its appeal had been allowed and would "provide further updates to the local community as the project progresses towards construction".