Energy and property firm the Banks Group secured consent on appeal in 2015 for the Bradley opencast coal site in Pont Valley, County Durham.
According to the firm, the site covers 71 hectares and the amount of coal due to be recovered is around 500,000 tonnes. Work to extract the coal began last year.
But, following the approval, campaigners argued that the secretary of state should use powers under section 100 of the Town and Country Planning Act to revoke the permission. This was refused by the minister in July last year.
A judicial review was then brought by local resident June Davison against Brokenshire's decision.
Davison argued that the secretary of state had failed to justify his decision to allow the mine to proceed given that another proposed mine near Druridge Bay in Northumberland was rejected by his predecessor Sajid Javid in 2018 on the grounds that it was incompatible with the UK’s climate change commitments.
Javid's decision was overturned at the High Court in November and Brokenshire will now have to reconsider the application.
A letter sent to campaigners from the government's legal team admitted that department had failed to take into account campaigners’ and lawyers’ letters that had raised comparisons between Bradley and the proposed Druridge Bay opencast coal mine.
The letter conceded there was a "flaw in the original decision-making process" and the decision would be "reconsidered by the secretary of state on a proper basis".
According to a statement from campaign group Desmog UK, Brokenshire will have until 25 February to make a fresh decision on the Bradley project, after which the judicial review can be reopened if a new decision has not been made.
Banks Group is also seeking an extension to the country’s largest opencast mine on land owned by Lord Matt Ridley in Northumberland (Shotton) and is investigating another coal site near Newcastle.
The Ministry of Housing, Communities and Local Government (MHCLG) was approached for comment but it had yet to respond at time of publication.