It's not every day that we get to quote Sir Issac Newton. But in the present economic climate his famous third law, that for every action, there is an equal and opposite reaction seems apt.

In the recent go-go years of easy credit, British consumers acted with impunity, racking up debts of some £1,000 billion. Now the banks are reacting with gripes over their customers' creditworthiness.

This morning, Barclays warned that "the slowdown across the UK consumer credit sector resulted in a rise in potential credit risk loans". In other words, shoppers have been hit by rising interest rates and some big spenders cannot pay off their plastic.

Barclays credit-crunch concerns echoed similar comments from HSBC last week. Barclays further disappointed its shareholders by highlighting a "weaker" showing from its mortgage arm, adding to a string of signals suggesting higher borrowing costs have taken the steam out of the property market.

Last week, the British Bankers Association reported that for the first time since May 1994, credit card debt was reduced, as cardholders paid off £40 million more than they borrowed. The data accompanied a string of disappointing retail sales figures from the likes of Next, Boots and Sainsbury, which further points to those same consumers opting not to buy products, and certainly not to extend their plastic.

After the credit boom, it would be natural to expect a bust. But the banks are pushing a theory that consumers will be insulated by a healthy UK economy. Barclays' finance chief, Naguib Kheraj, said today that the deterioration in consumers’ ability to repay their debts would be tempered by benign conditions.

"Most commentators still expect GDP growth for the year of 2 per cent to 3 per cent, which is pretty healthy, while interest rates and unemployment are historically low ... we’re comfortable with the outlook, but not complacent," he said.

The CBI was not so upbeat. The organisation painted a mixed picture in its Economic Forecast. But it was quite sure the impact of last year’s interest rate rises will "continue to feed through, alongside a cooling housing market".

The employers' organisation also pointed out that "a significant minority" of households will face much higher mortgage payments as two-year fixed rate terms, taken out when base rates were at their trough in 2003, come to an end.

Not to worry, says one school of thought pushed by the champions of the ailing manufacturing sector. A little monetary tinkering, a dab on the accelerator in the shape of a cut in interest rates will steer the UK through this "difficult" patch. Such a course would also, happily, provide consumers with some relief on the credit card bills and mortgage repayments.

This would be fine if it were not for rising prices. Inflation has risen steeply from 1.1 per cent in September to 1.9 per cent in April. Higher fuel costs are expected to push inflation higher in the near-term, peaking at 2.2 per cent in the fourth quarter of this year, according to the CBI. With a remit to target 2 per cent on a two-year horizon, The Bank of England may well be nervous of lowering the cost of borrowing if inflation shows no sign of moderating.

So anybody thinking of splurging on their credit cards might do well to remember that one last rule of physics might not hold when it comes to interest rates: what goes up does not always come down.

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