Almost 90 per cent of consumers plan to shop online for Christmas presents this year, with 44 per cent preparing to scoop bargains on eBay.
Only 11 per cent said they would go to the high street instead, according to research by web testing specialists SciVisum.
But in an indication that online service is crucial, a huge 95 per cent said they would abandon websites if performance was not up to scratch, and 55 per cent would not give the website a second chance.
The main reason for abandoning a website was sluggish performance, cited by 78 per cent; almost 76 per cent said they would not wait more than a minute for pages to respond before abandoning a site.
The biggest annoyance for customers was complicated website registration processes, which 74 per cent found a turn off.
The research also found that that the majority of e-retail sites failed to prepare their infrastructure for Christmas last year.
"Bargain hunters will be flocking to the web in droves this Christmas," said SciVisum chief executive Deri Jones.
"But our study shows that UK consumers are not willing to tolerate poor performance, or give sites a second chance. E-tailers can expect a season of bad will from consumers if they don't take action now to prepare their websites for the Christmas rush."
The Christmas period is likely to test online retailers' websites to the limit. SciVisum estimates that shopper numbers will increase by 12 per cent during the Christmas period, with the biggest number logging on to buy presents in the first week of December.
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