Carphone Warehouse has been fined 245,000 pounds over failings in its sales of mobile insurance over the telephone.
The Financial Services Authority said that between January and October last year Carphone failed to send some of its telesales customers documents and policy summaries to help them understand what they were buying.
The retailer also failed to notify the FSA until October, though it was aware of the problem in March, the FSA said.
The Carphone Warehouse Ltd failed its telephone sales consumers by not giving them all the information necessary for them properly to understand the insurance product they had bought, said Sarah Wilson, the FSA's director of retail firms.
But the retailer said the fine was surprising and disproportionate, adding its customers had not suffered as a result of the problems in what Carphone said was its smallest sales channel.
We take every aspect of service and administration very seriously. The FSA response does, however, feel a bit like a sledgehammer to crack a nut, Carphone Chief Executive Charles Dunstone said in a statement.
Our intention has only ever been to work within the FSA regulations, and, being new to regulation of this kind, there has been a period of adaptation and learning. Our priority remains to continue to offer our customers the best insurance policies on the market.
The FSA said Carphone had agreed to carry out retrospective mailing for consumers affected and was committed to carrying out a comprehensive review.
Carphone said there had been no impact on customers' policies, cover or ability to claim.