Business and Energy Secretary Grant Shapps said 'the public have a right to know' as he revealed which companies have the lowest winter discount redemption rates.
National Grid has said it is firing up coal power stations that are otherwise on standby - with scores of energy firms taking part in a Demand Flexibility Service to curb the nation's usage.
The sale of wood burning stoves is on the up as figures show 10,000 more people have already opted to have at least one fitted in their homes before the cold winter hits.