Up to half a million Barclaycard customers have had their spending limits cut since last year.
The UK's biggest credit card issuer, with 10 million customers, has also tightened the criteria for people applying for cards.
Barclaycard said it was trying to reduce the level of bad debts and denied its move had been prompted by the crisis in the world money markets, which has made it harder for some lenders to raise cash to offer new cards, loans and mortgages.
"This is something we have been doing since early 2006," said a Barclaycard spokeswoman. "We are simply looking to cut bad debt."
In some cases, the company said, it was leaving people's credit limits unchanged – instead reducing the amount of cash they could withdraw on their cards at ATMs.Reuse content