Thousands of people have been charged more than double the correct amount on their gas bills because of basic errors in meter readings by energy companies, industry executives have declared.

Firms failed to apply the conversion rate between cubic feet and cubic metres when new metric gas meters were installed, Ofgem found. The industry regulator said it had written to companies about the mistake.

Some  may have overpaid by 130 per cent  while others could have underpaid by 60 per cent, industry experts told the Financial Times.

Energy UK, the industry body, said it was working with companies “to investigate and address a gas metering issue” which had potentially affected “an extremely small number of accounts”.

“Anyone who has been affected will be contacted directly and any incorrect billing or charging will be sorted out as quickly as possible, including any refunds where necessary,” it said.

An Ofgem spokesperson said: “Ofgem is working with suppliers to ensure consumers don’t lose out. This includes suppliers setting out plans to redress their affected customers, and to reach a quick resolution.”