An application was submitted last year to deregister a 244-hectare parcel of common land at Trefil Las and Twyn Bryn-March Common and provide replacement land comprising 307 hectares of new common land across seven sites.
The application was made to allow the Circuit of Wales motorsport facility near Ebbw Vale to go ahead. The project includes a series of circuits alongside hotels, retail space, industrial and businesses space, landscaping and parking facilities.
The application to deregister the land was called in for a public inquiry in April 2014. The development had been granted outline planning consent by Blaenau Gwent County Borough Council in July 2013.
Last week, Welsh Government deputy minister for farming and food Rebecca Evans approved the deregistration and exchange of common land application.
A statement from Blaenau Gwent Council said the decision paves the way for fresh planning applications to be submitted for phase 1 of the motorsport scheme.
"The council is working closely with the developer’s consultants with a view to submission by early 2016. When received, these applications will be the subject of extensive publicity and consultation", the council said.
However, Kate Ashbrook, general secretary of conservation body the Open Spaces Society, said the deregistration decision was a "black day for common land". She added: "We believe that the public will permanently lose out as a result of this decision."
"We are appalled that the minister concludes that it is acceptable to sacrifice a square mile of open hillside, where people have rights to walk and ride, on the edge of a national park in exchange for seven much smaller areas scattered some distance away, where either there is already public access by right or custom or the land is inaccessible," said Ashbrook.