The boss of a North-East charity who has backed a national call to protect customers said last night: "You should not be seen as a sucker for being loyal".

Neil Bradbury, CEO of Citizens Advice County Durham said the poorest people in the North-East are being penalised for being loyal customers.

Mr Bradbury said it was "ironic" that those with the lowest incomes were often paying the most for their utilities simply because they did not have the resources to make a switch.

These loyal customers are now at the centre of a super complaint lodged by Citizens Advice to the competition watchdog after the charity found those who remain loyal are being penalised by £4billion a year.

The national charity said the practice of overcharging loyal customers was widespread and called on the Competition and Markets Authority (CMA) to "act now to stop people being exploited".

It's research showed that consumers are losing across the five essential mobile, broadband, home insurance, mortgages and savings markets to the "loyalty penalty", with eight in ten people paying a significantly higher price to at least one of their providers for remaining with them.

It found the loyalty penalty is on average £877 per year - equal to 3 per cent of the average household's total annual expenditure.

And while the Government's price cap in the energy market would bring down loyal customers' bills by £75 per year on average, "excessive prices" for those who remain with the same provider in other markets could be just as high, if not more so.

The charity also found the loyalty penalty is disproportionately paid by vulnerable consumers such as older people and those with mental health issues - groups that are particularly likely to struggle with switching.

In County Durham alone, Mr Bradbury said the service had helped 1,612 with energy issues in the last year alone and this month was their busiest since records began.

"We do a lot of work with people about switching and I think a significant percentage of people are still with the same provider," he said. "People are suffering from this and I suppose our experience in the North-East, if anything, is that the problem is slightly higher."

Mr Bradbury said the people the service had helped were only the "tip of the iceberg" and it was affecting people of all ages, particularly those who were vulnerable.

Another example he used was the fact that people are often still paying for their mobile handset, after their initial contract has been paid off.

"You should not been seen as a sucker for being loyal," he said.

A super complaint can be made by a Government-designated consumer group to ask a regulator to investigate an issue or a market that it believes is working against the public interest.

The regulator must publicly respond to the complaint within 90 days saying if it believes it is an issue and if so how it intends to deal with it.

Citizens Advice chief executive Gillian Guy said: "It beggars belief that companies in regulated markets can get away with routinely punishing their customers simply for being loyal. As a result of this super complaint, the CMA should come up with concrete measures to end this systematic scam.

"Regulators and Government have recognised the loyalty penalty as a problem for a long time yet the lack of any meaningful progress makes this super complaint inevitable.

"The loyalty penalty is clearly unfair - 89 per cent of people think it is wrong. The CMA needs to act now to stop people being exploited."

The CMA confirmed it would investigate the concerns with regulators such as the Financial Conduct Authority and Ofcom and publish a response within 90 days.

CMA senior director Daniel Gordon said: "We will now carefully consider the concerns raised by Citizens Advice, and any further evidence on this issue.

"Our response will set out the CMA's views on this important issue and any next steps we think are needed to make sure businesses don't take unfair advantage of their long-standing customers."

For help visit citizensadvice.org.uk