A grouse shoot near Hebden Bridge is at the centre of legal action against the UK government over the burning of bog land habitats.
The European Commission has issued legal action following complaints about burning of blanket bog at the Walshaw Moor estate.
The sponge-like bog provides a natural habitat for birds and other species and helps prevent flooding by absorbing rain water.
Environmentalists say burning it off increases the risk of flash flooding because rainwater flows moor quickly into streams and rivers.
The RSPB and action group Ban the Burn previously complained about an agreement drawn up four years ago between Natural England and the 6,500-acre grouse shooting estate.
Now the European Commission is investigating whether environmental rules have been breached in relation to Walshaw Moor and other sites around England.
An RSPB spokesman said: “The complaint emanated from growing concerns we had about the way that the estate was being managed.
“Burning of blanket bog is systemic across large parts of English uplands.”
A Letter of Formal Notice in relation to “Bad application of Habitats Directive to blanket bog habitats in the English SACs (Special Areas of Conservation)” is listed on the European Commission’s website.
A spokeswoman for the Commission said the action was at the pre-litigation stage and a remedy would be sought to avoid court proceedings.
She added: “We can confirm that the Commission is investigating a possible breach of the Habitats Directive, in particular the practice of burning blanket bog habitat in the English special areas of conservation including at Walshaw Moor.”
The formal notice letter was not publicly available.
The Department for Environment, Food and Rural Affairs (DEFRA) confirmed the formal notice had been received, but could not comment further on ongoing legal action.