The energy regulator Ofgem could fine the energy company up to Â£1.2bn for failing to meet its carbon emissions reduction target (CERT) set by the Government.
It is understand that the firm failed to meet a deadline to reach the designated amount within the December 2012 limit.
Ofgem can fine companies such as British Gas ten per cent of their turnover if they fail to deliver adequate figures for CERT and other energy efficiency schemes.
However, it is expected that any fine the company does take will be somewhat smaller due to a variety of mitigation measures including late delivery and the meeting of overall energy efficiency targets.
British Gas is part of the 'Big Six' energy firms, all part of the Warm Home Discount Scheme, who were all set targets to meet by the Government in regards to boosting energy efficiency in their customer's homes.
Out of the 'Big Six', only four of the suppliers - E.On, EDF, Npower and SSE were able to say that they had met all the targets that had been set. Scottish Power on the other hand, could only confirm that it had met the firm's overall target.
British Gas was confident of meeting carbon saving measures elsewhere however.
British Gas new energy managing director, Jon Kimber, said: "We are confident we will have met our total targeted carbon savings across all our environmental obligations, after taking into account the latest guidance published by Ofgem.
"In meeting these targeted carbon savings we will have delivered more benefits to vulnerable customers than was originally envisaged by government."
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