Small and medium-sized businesses have been losing out on energy deals compared to big businesses, according to data released by the Forum of Private Business (FPB).

The latest industry data available from the government shows that average electricity prices for small and medium sized firms increased by 15-17% between the third quarter of 2008 and the same period of 2009. However, prices increased by 9-11% for large businesses and by just 5% for the UK's biggest companies.

According to the figures from the Department of Energy and Climate Change average non-domestic gas prices went up by 8% for the smallest businesses but fell by between 14 and 52% for all other commercial customers.

"While the big energy companies always pass on wholesale price increases in full the same cannot be said when prices fall. This is the tip of the iceberg. By refusing to play fair some utilities giants have forced costs on small businesses they can ill afford," said the FPB's Finance Director Nick Palin.