Christmas trading at a raft of online retailers including Lovefilm.com and Sportsdirect.com was affected after online payments service provider Sage Pay experienced technical problems on Monday night.
The company said the problems started at around 6pm and were resolved by around 10pm, and were caused by a combination of software and hardware faults.
Sage Pay managing director Simon Black said it was an isolated incident but admitted it had happened on one of the busiest days of the year for online retailers.
He said: “It was one of the worst times of the year for it to happen. If the same thing was to happen again we’d be able to resolve it very quickly.”
He added that some retailers had been able to get in contact with consumers and take payments for purchases in other ways.