MORE Scots are using credit cards to pay off their fuel bills, sparking renewed fears over debt levels.
The latest research for the Debt Advisory Centre Scotland found 12.5% of settled a utility bill with credit last month - up from just 4% in summer 2013.
The figure is equivalent to some 600,000 people in Scotland paying for gas and electricity on credit.
However, the figures for Scotland are better than the UK as a whole, where nearly one in five people borrowed to pay for their gas, electricity or water.
This represents more than a three-fold increase on the 5% who did so over July and August 2013.
Ian Williams, a spokesman for the Debt Advisory Centre Scotland, said: "It's a real concern to learn that three times as many people in Scotland have had to use credit to pay for their gas or electricity this year than did so seven months ago.
"The fact that more than one in 10 Scottish bill-payers have had to rely on credit seems worryingly high. It's troubling that people appear to be increasingly using credit so they can pay for something essential like their energy bills."
Mr Williams said that, instead of using credit, consumers should seek help to manage their debts.
The rise in credit card payments comes as new figures show energy complaints have soared in the first three months of the year - a 224% rise on the first quarter of 2013.
The energy sector's ombudsman said that, between January and March, complaints trebled to 10,638, compared with 3277 received during the same period last year.
The numbers suggest 2014 will see more complaints overall, with 17,960 complaints made over a 12-month period last year.
The latest figures from Ombudsman Services come after regulator Ofgem said it was referring the sector to the Competition and Markets Authority for a full-scale competition inquiry.
The ombudsman figures show more than 2000 consumers complained about not receiving bills, while 1474 people made complaints about charges. More than 1000 consumers criticised the quality of customer service.
Lewis Shand Smith, the chief energy ombudsman, called for increased transparency in the wake of the figures.
He said: "Consumer frustration and dissatisfaction is something that we hear about every day, and we welcome any attempts by Ofgem to make the energy market fairer.
"With energy complaints trebling in the first quarter of this year and problems relating to billing the greatest concern, increased transparency is something that should be addressed."
A spokeswoman for Energy UK, the trade body that represents the industry, said most customers had no problems with their energy company, but accepted that sometimes things go wrong.
She said: "If a customer has any concerns relating to their bills, they should contact their provider as soon as they can and, if possible, have an up-to-date meter reading to hand which will ensure their bill is as accurate as possible.
"Energy companies work very hard to resolve problems and most complaints are fixed within a few working days with no more than a phone call."
The spokeswoman said there were new rules in force that ensured bills were explained to people, it was easy to switch suppliers and also to ensure customers were on the best deals.
SSE, one of the so-called Big Six companies, said it was listening to customers' concerns and was committed to freezing prices until at least 2016.
A spokesman said: "We have also made improvements towards our customer service, including the introduction of a guarantee that gives money back to customers if we fail to meet promises."