Barclaycard has cut the credit limits of half a million of its customers to reduce the number defaulting on their debts.
The credit card provider has also tightened its criteria for new customers and is monitoring existing cardholders carefully.
The group said the strategy, which it began last year, aimed to cut the level of bad debt it incurred.
Barclaycard said it was looking at customers on a case by case basis and is using information available to it from other lenders under new industry data-sharing initiatives.
In some cases it said it was leaving people's credit limits unchanged, but reducing the level of cash advances they could get with their card, as there is evidence to suggest that people who use their credit card to get cash are more likely to be struggling with debt.
The group said it is also using a so-called "low and grow" approach to some new customers, under which it gives them a low initial credit limit, but increases it when they show they can manage the debt. A Barclays spokesman said: "Barclaycard undertook a review during 2006 of the credit limits of our customers.
"This resulted in us reducing the credit limits of some 500,000 customers where we had information which led us to believe that these customers may be experiencing difficulties in repaying their total borrowings.
"We also shared more data within the industry, slightly reduced the percentage of new applications for cards we accepted to approximately 50 per cent and a number of other initiatives which have reduced the number of our customers experiencing difficulties."
But the group stressed that its actions did not have anything to do with the current credit crunch which led to the recent problems at Northern Rock.
Barclaycard said its strategy had led to a nine per cent fall in provisions for bad debt during the first six months of this year, with the amount of money it needed to set aside to cover people defaulting on their borrowings dropping to #443 million.