Plans to create a biomass plant, which would create 560 jobs in Pembrokeshire, have been put on hold.
Egnedol wants to invest £685m in a renewable energy facility at the former Gulf refinery at Waterston and the RNAD Blackbridge site in Milford Haven.
But Planning Inspectorate Wales has suspended the Cypriot-owned company's application for six months.
It said it had provided "inadequate" information on several protected species and habitats.
The plant would see biomass converted into a biogas, which would be used to produce green electricity or green liquid fuels.
The planning inspectorate has written to Egnedol to say it was going to "suspend the examination" of its planning application until 30 September 2017.
It said the company's environmental statement is "inadequate" in respect of the effects the biomass plant would have on protected species and habitats, and urged it to carry out further assessments.