The "big six" energy firms made an average profit margin of 20 per cent for energy generation in their last financial year, according to figures released by energy regulator Ofgem.
The results are likely to fuel further anger over rising gas and electricity bills.
The key figures included:
- Profits in the domestic supply business increased by 75 per cent
- Companies made on average £53 per customer each year
- Average profit margins increased from 2.8 per cent to 4.3 per cent in 2012
- The big six made an average profit margin of 20 per cent for energy generation in the last financial year