Shares in Experian, the credit-checking group, dived by 7 per cent yesterday as investors took fright at the company’s exposure to the troubled American sub-prime mortgage market and cautious UK lenders.

Experian, spun out of the GUS retail conglomerate, reported group sales, excluding gains from acquisitions, up by 6 per cent in the half year to September 30.

However, the group conceded that revenue growth would have been 8 per cent if Lower My Bills, its American home-loans price comparison website, had not been hit by stagnation in the US sub-prime market.

Experian also said that its credit services division — its largest business, contributing 44 per cent of annual revenues — had been affected by the “accelerating decline in mortgage origination”.

The group’s shares closed down by 38p, or 7 per cent, at 505p, below the 560p float price when it came to market as an independent company almost exactly a year ago.

However, the company said it had offset weakness in its US credit services by providing other services to banks as increasingly cautious lenders focus on managing their existing debtor books rather than issuing new loans.

Experian gets a commission from lenders whose websites are accessed through Lower My Bills. They also pay Experian for a credit check on customers who click through.

However, Paul Brooks, Experian’s chief financial officer, said yesterday that the US mortgage market had come to a standstill, and that sub-prime borrowers who were tempted to take out mortgages on two-year low-payment offers were now struggling to refinance the debt.

In the UK, the company said: “The market environment for UK financial services is challenging, affecting Experian’s credit and marketing-related activities.”

More than half — 53 per cent — of Experian’s global client base is made up of financial services companies. But the group said it had increased other areas of its credit services, such as account management and debt collection, and interim sales had increased.