Post-Brexit economic uncertainly means the 19 million people who don’t clear their credit card balance every month could be sitting on a financial timebomb.

It was 50 years ago this summer that Barclays Bank issued the UK’s first cards and, used wisely to spread the cost of major purchases, they have been a boon for consumers ever since.

However, with interest rates on plastic at an all-time high and Bank of England Governor Mark Carney warning about how the UK’s vote to leave the EU could affect ordinary consumers, many may soon be wishing they hadn’t spent so much.

Introducing the Bank’s latest Financial Stability Report this week, Mr Carney highlighted the need “to identify clearly the risks to financial stability and be straight with the British people about them”.

He said: “UK households and business who want to seize viable opportunities in a post referendum world can be confident they will be supported by the financial system.”

However, he went on to warn: “The number of vulnerable households could increase due to a tougher economic outlook and a potential tightening of credit conditions.

“In particular, there is growing evidence that uncertainty about the referendum has delayed major economic decisions, such as business investment, construction and housing market activity.”

When the economic outlook deteriorates, banks and others tend to raise their interest rates and become more choosy about who they lend to.

As a result, many borrowers could struggle to meet their repayments, particularly if they fall casualty to a declining jobs market. They could also find it increasingly difficult to get alternative credit at an affordable rate.

New figures from The Money Charity show that at the end of May, UK consumer borrowing, excluding mortgages, was £184.3billion. That is an average of £6,825 per household, £387 more that in May 2015, and much of it is on cards.

MoneySupermarket.com says 70 per cent of the UK’s 52m adults have at least one a credit card, and 19m of them can’t afford to clear what they owe at the end of the month. Some have been in debt for as long as ten years.

Despite the Bank of England’s base lending rate sitting at a record low of 0.5 per cent for seven years, the cost of borrowing on plastic has never been higher. According to Moneyfacts.co.uk, the average annual percentage rate of interest charged on card purchases is a staggering 22.3 per cent – up from 21.2 per cent a year ago.

Anyone concerned about the amount of interest they are paying, or whether they could cope if rates rise further, should consider moving their debt to a lower cost alternative as soon as possible.

Kevin Mountford, banking expert at MoneySupermarket, said: “We’ve come a long way since the first credit card was created 50 years ago. Now there is a huge variety of products to suit different types of spending, and consumers have been able to benefit from increasing rivalry between providers.

“The balance transfer card market has been extremely competitive with providers increasing the duration of the fee-free period and cutting fees. It’ll be interesting to see how much longer this competition can last, but consumers should make the most of the deals whilst they can.”

The interest savings can be significant. Rachel Springall, finance expert at Moneyfacts.co.uk, explained: “Borrowing £4,000 on a card charging an annual percentage rate of 18.9 per cent will cost £1,097 in interest and the debt would linger for two years and 10 months if a repayment of £150 is made each month.

“However, if a borrower opted for a credit card charging 6.4 per cent, the lowest rate currently on the market, and made the same repayment, they would save £780 in interest. And if they used the best interest-free credit card and paid back the debt before the offer ended, then they could avoid accruing interest charges altogether.”

Halifax is currently offering the cheapest balance transfer deals on the market. It has a card charging no interest for 24 months with no transfer fee, and another, with a 2.49 per cent fee, which charges nothing for 40 months.

Other providers, including MBNA, Virgin, Tesco and Sainsbury’s banks, also have cards that charge no interest for 40 months but with slightly higher fees.

Once you have moved your debt, to save the maximum amount of cash, ensure the balance is cleared within the interest-free period. If this isn’t possible, and you can’t find another low-cost transfer deal, the remaining debt is likely to attract a rate of 18 per cent or more.

For those looking to make new purchases, the cheapest providers currently include Sainsbury’s Bank, which is offering 27 months interest free, while the lowest long-term purchase rate – of 6.4 per cent – is available from the AA.

But while the economic outlook is uncertain, be wary of spending cash you might later have difficulty repaying.

Ms Springall said: “The real danger with credit cards is that consumers can become too comfortable with debt. Larger credit limits mean that it’s too easy to innocently increase the amount of money owed, and this can lead to a never-ending vicious cycle of debt.”

If you are worried about repaying what you owe, get help from an impartial expert now. The Money Advice Service’s website, moneyadviceservice.org.uk, has clearly written sections on taking control of your debt.

Other sources of free help include charity StepChange (stepchange.org or 0800 138 1111), the National Debtline (nationaldebtline.co.uk, mymoneysteps.org or 0808 808 4000) and the Debt Advice Foundation (debtadvicefoundation.org or 0800 043 4050).

CASE STUDY

If you have a clean bill of financial health, and don’t even own a credit card, you could find borrowing tricky. So Robert Shaw from West Kilbride took a different route when buying his BMW 4 Series. “I didn’t have a credit rating because I didn’t have a credit card. I would be penalised because I didn’t have that history.” Mr Shaw discovered Scotwest credit union, signed up as a member after sending them three months of wage slips and bank statements, and borrowed what he needed at 4.5 per cent. He says: “I looked at the interest rates I would pay on finance, and Scotwest was by far the best at the time.” Membership of Scotland’s 100 credit unions grew by four per cent to 375,000 last year.