They say there is an “appalling lack of information” handed out to users by energy suppliers, and three quarters of people are unaware of hidden charges that come with them.

Bureau manager Sue Green said: “It is our view that many vulnerable households are finding things even harder because of their prepayment meter, and we have a number of recommendations for change to address this unfair situation.”

The Stratford branch conducted an extensive survey into prepayment users in the district, asking hundreds of people using energy cards and keys what they knew about their fuel supply. What they found shocked them.

“We were concerned by the spiral into debt and fuel poverty that was increasingly becoming the hallmark of CAB clients with PPMs and the failure of energy suppliers to put them on a level playing field with those on credit meters,” said Sue.

The branch recently published a damning 20-page report – Left out in the Cold: Why prepayment meter users need a better deal – and launched a campaign to get energy suppliers and the government to change the situation.

Users are often those living on the breadline. Research found less than a third of people on prepayment meters are working, the rest dependent on benefits or pensions. Three-quarters of people (74 per cent) did not realise around 28p a day was deducted from the money they topped up.

Although prepayment meters are designed to help impoverished people in fuel debt repay arrears, more than half (53 per cent) of the people surveyed inherited their meter, having moved into a property where it was already installed.

Mum-of-three Ceri Durrant, aged 38, lives in a two-bedroomed Orbit Heart of England social housing property in Lighthorne Heath with her family. Her husband Jeremy, 35, works full-time as a production co-ordinator in Southam while she works part-time at the local children’s centre.

Before she went to the bureau for help last winter she was putting between £40 and £50 a week on her electricity key.

“I feel like you’re closely watching it because you’re constantly thinking have I got enough electricity,” she said.

Ceri's prepayment meter

She was on a tariff called Economy 7, designed for people with night storage heaters. It has a high daily rate and low rate for electricity consumed between midnight and 7am. However, none of Orbit’s properties in the village have ever had night-storage heaters and so for five-and-a-half years all Ceri’s energy usage was taking place at the most expensive rate without her knowing.

“I just thought Economy 7 was the cheapest tariff to be on to be fair,” she said.

The bureau got Ceri to change her tariff with E-On but they want energy suppliers to offer prepayment meter users with a wider range of tariffs as well as the opportunity to remove the meter.

Ceri said: “Ideally we’d like to get rid of the PPM and go direct debit but you have to pay for that privilege.” It can cost between £50 and £200 to transfer to a credit meter, a service the bureau want energy suppliers to offer for free.

To make matters worse, in Lighthorne, the only place to top-up is at the post office in the village hall, but this is only open between 11am and 2pm, three days a week. If users want to top-up outside these times they have to drive or get the bus to the next village.

Marilyn Price, who put the bureau’s report together, is heavily critical of the impact prepayment meters has on people in the Stratford district.

She said: “The lack of choice has been a consistent theme throughout our survey.

“As they have made very clear, the only choice many of our PPM users have is ‘eat or heat’.”

Main findings of the survey

75%of respondents found it difficult to pay for gas and electricity.

64% found it difficult to pay for food.

Less than a third (31%) of the respondents were working, and half of these received Working Tax Credits. The remaining two-thirds lived on benefits or pensions.

74% did not know that standing charges were deducted through their meter.

62% lived in a housing association or council property.

53% of households inherited their prepayment meter.

67% needed to use emergency credit in colder weather and single parents were the most frequent users, using emergency credit five times a week.

62% of respondents were in debt, owing an average of £3,840 per household.

(Results based on a sample of 334 people from the Stratford district took the survey between November and December 2012.)