Now comes the first hard evidence that customers have voted with their feet - with 62,000 leaving the energy firm.
An ITV News investigation has revealed that many charities are overpaying on energy bills, but how can the organisations reduce their costs?
An investigation by ITV News has discovered that many charities are being charged too much on their energy bills.
The Conservatives have accused Labour of bringing Britain's economy to its knees, after it announced proposals to revoke energy companies' licences helping protect the interests of the public. A Conservative Party spokesman said:
– Spokesman, Conservatives
Labour left our country with a broken energy market and huge taxes on bills - meaning the number of people in fuel poverty nearly doubled in Labour's last five years.
We've been taking action to put this right. We've taken £50 off the average bill by rolling back green levies. We're carrying out a full, independent inquiry to fix the broken market we inherited. And we're forcing energy companies to simplify bills so people can be sure they are getting the best deal.
A new energy regulator would be charged with producing an annual scorecard for energy suppliers, reporting on the company's performance and identifying any possible areas of concern, Labour has announced.
Shadow energy and climate change secretary Caroline Flint said: "The public have a right to be treated fairly by energy companies. Where firms fail to meet these standards, there must be tough and decisive action. Too often energy companies seem to view the regulator's fines as a cost of doing business - not as a warning to get their act together.
"Of course consumers must be compensated - but if energy companies persist in mistreating their customers they must know their licence could be on the line."
A Labour government would give a new energy regulator the power to revoke energy companies' licences to help protect the interests of the public, the party announced today.
Shadow energy and climate change secretary Caroline Flint accused the Government of presiding over a "broken energy market" and said Labour would hand a tough new regulator the capability to cancel energy companies' licences where there were repeated instances of the most "serious and deliberate breaches of their licence conditions which harm the interests of consumers".
Figures obtained under the Freedom of Information Act, she claimed, showed energy companies had continued to "mistreat their customers" and face another 16 probes into mis-selling, poor customer service and other bad practice, despite Ofgem issuing 30 fines, totalling more than £87 million since 2001.
A treasurer at a village hall, which holds events for good causes, told ITV News energy companies should take responsibility on reducing power bills for registered charities.
Val Belton told ITV News: "I think it should be down to the energy companies to raise this question with you particularly when the bill is for Burpham Village Hall - they may think 'maybe that's a registered charity, I'll clarify whether they are'."
An ITV News investigation has shown that many charities are being over charged on their electricity bills.
We asked HMRC how charities can get a refund and whether they accept some charities are missing out on reduced energy bills. Here are their responses:
Does HMRC accept that many charities which are entitled to reduced VAT are missing out?
– HMRC statement
No, HMRC believes that the vast majority who are entitled to receive the reduced rate of VAT and CCL exemption. With millions of supplies made by fuel and power companies, it is not possible for HMRC to determine that every supply is taxed correctly. Ultimately though, the responsibility lies with the individual charity.
How does a charity get a refund for overcharged VAT?
– HMRC statement
If a charity believes it has been charged the wrong rate of VAT on a supply of fuel and power, or that it has been charged CCL, it should contact its supplier and request a refund.
Organisations need to tell energy suppliers they are registered as a charity so the correct tax rates can be applied, Energy UK told ITV News.
The advice comes after an investigation by ITV News showed many charities are overpaying on their energy bills.
– Energy UK statement
When charities register with the Charities Commission it is vital they are told all the benefits to which they are entitled and how to apply.
It is not always obvious from the name that an organisation may be registered as a charity and suppliers can only know if they are told.
Charities should get in touch with their supplier so the appropriate tax rates can be applied. Suppliers want to help where they can and take their responsibility to their customers seriously but are unable to do so if they don’t have all the facts.
Under current HMRC rules companies cannot pay back more than four years of VAT.
Plans to make it a criminal offence to manipulate the energy market will provide a "stronger deterrent" against the practice, Energy Secretary Ed Davey said.
Anyone found guilty of rigging wholesale gas and electricity prices could face up to two years in jail under new proposals.
"Manipulating the energy market is absolutely unacceptable, and these proposals provide a much stronger deterrent - more in line with the approach taken in the financial markets," Mr Davey said.
The Energy Secretary said the government was doing "everything it can to help consumers" with their energy bills.