A conservation group says a music festival at a wildlife haven has been given the go ahead without a full understanding of the risk to rare species.

The Wren Conservation Group has written to the City of London Corporation to express its “serious concern” that a proposed festival on Wanstead Flats came one step closer to reality this week.

No date has yet been set for the as yet unnamed three-day festival, organised by entertainment company MAMA Festivals Ltd, which could see up to 50,000 revellers flock to the beauty spot.

Despite the City of London Corporation this week granting its approval for the event, the festival cannot go ahead unless Redbridge Council grants organisers the relevant licences later this year.

The Wren group fears for the wildlife living on Wanstead Flats.

A spokesperson said: “Just a couple of years on from the worst grass fires in London’s history on the same site, we find it extraordinary and worrying the City of London, the custodians of the rich but fragile habitats found locally, would conduct a vote based on such an obviously incomplete picture of the likely impact on local wildlife.

“The remaining, and undamaged, wild areas of the Wanstead Flats are fragile and under great stress. Despite being the closest remaining location to central London, where skylarks breed and can be heard singing, there are only five or six pairs left breeding here.”

Skylarks are a rare ground-nesting breed of bird and are just one of the many protected and declining species that call Wanstead Flats their home.

The Wren Group fear these creatures could be put “in peril” by the party-goers coming to and from the festival.

The group will also raise its concerns “urgently” with local councillors and MPs.

A spokesperson for City of London Corporation said: “Elected Members have agreed in principle that the event can be held at the site.

“The event organisers will now need to apply to the London Borough of Redbridge for a licence to hold the event and conduct a full public consultation.

“They will also be required to mitigate against any environmental issues in order for the event to go ahead.

“Epping Forest is a registered charity and if the event were to proceed, all surplus income will be reinvested in the management of the Forest.”

A Redbridge Council spokesperson confirmed the authority is aware of the plans and reiterated that the event organisers must apply to the council directly for an alcohol and entertainment licence in due course.

Following a public consultation, and consultation with local police and fire teams, on the proposals for the festival, the authority will have the final say on whether or not the festival can go ahead.