The news will come as yet another major blow to Westbury Town Council and Westbury Gasification Action Group/No Westbury Incinerator who have objected strongly to the controversial scheme.
Debra Urch, town clerk at Westbury Town Council, said: "We will be consulting with our lawyers and looking to challenge Wiltshire Council's strategic planning committee. "We will seek advice from our solicitor and, if necessary, will take it back to council for a decision on what to do next."
On April 20, Wiltshire Council's strategic planning committee voted to postpone its final approval on a change to the operating equipment for the proposed incinerator pending the Environment Agency's decision on the operating permit.
In March, Michael Gove, the Minister for Levelling Up, Housing and Communities, sparked anger in the town when he refused to 'call in' the NREL plans following a request by local MP Dr Andrew Murrison.
In a letter to Westbury Town Council, the Environment Agency said: "Thank you again for submitting your comments to the second consultation on the permit application for Northacre Renewable Energy Ltd (NREL) to operate an energy from waste incinerator in Westbury.
"We have decided to grant the permit application to Northacre Renewable Energy Ltd.
"We understand that you may be disappointed with this result and want to reassure you that the permit will ensure that robust levels of environmental protection are met.
"Our decision process is objective and based on NREL demonstrating that they have met, and will continue to meet, expected mandatory conditions as outlined in the permit."
It added: "Environmental law sets out these conditions, and as a regulator we are obliged to issue the permit if we can find no reason that the operator would not be able to comply."
The planning process and permitting process are separate and neither one depends on the other.
"We can issue a permit without planning approval and planning approval can be issued without a permit decision. However, NREL cannot start operating before both have been granted.
"The decision document explains in more detail how we have reached this decision. It also identifies the concerns raised in comments during our public consultation and how we have addressed these."
"We have issued NREL with their permit, which they will have to comply with if they begin operating."
NREL has already begun building work on its site next to the Northacre Resource Recovery Centre on the Northacre Industrial Park in Stephenson Road, Westbury.
They are allowed to do this under their planning permission, but they would not have been allowed to operate until the Environment Agency had granted the permit.
You can view the decision document and permit here.