British Steel is seeking a £100m loan from the government in order to meet EU emission rules.
Previously, the company could have used EU-issued carbon credits to settle its 2018 pollution bill.
However, the steel maker has been affected by a European Union decision to suspend UK firms' access to free carbon permits until a Brexit withdrawal deal is ratified.
Sources say there is no danger to British Steel sites or jobs.
The EU's emissions trading system's rules allow industrial polluters to use carbon credits to pay for the previous year's emissions, or trade them to raise money.
Each free permit gives a firm the right to emit a tonne (1,000kg) of carbon dioxide (CO2), and they can be traded for money.
In a statement the company said: "We are discussing the impact of Brexit on our business with ministers and officials from the Department for Business, Energy and Industrial Strategy and they have been extremely responsive and supportive to date."
The company is in talks with Department for Business about financial help.
The Department for Business, Energy and Industry Strategy told the BBC: "As the business department, we are in regular conversation with a wide range of sectors and companies."
British Steel has until 30 April to comply with EU emission rules.