More than two thirds (67 percent) of web users don't trust online retailers to deliver goods in time for Christmas, says Eptica.

According to the email management software developer's 2011 Retail Experience Study, 46 percent of Brits still plan to do last minute shopping online despite this.

Furthermore, the study revealed that 85 percent of the UK's top retail sites failed to provide straightforward details of final ordering dates to guarantee Christmas delivery. Eptica says this leaves consumers with no option but to puzzle it out for themselves based on standard delivery information or forces them to call or email already stretched contact centres.

"Given the economic situation this promises to be a hyper-competitive Christmas for UK retailers as customers shop around for the best deal," said Dee Roche, global marketing director, Eptica.

"The Eptica study shows that retailers need to do much more to reassure customers that their presents will arrive for Christmas day. Consumers obviously trust Father Christmas to deliver on time - but not the majority of online retailers."

Eptica said on average websites only provide the answer to half of all enquiries web users have when shopping online. Furthermore, less than half of firms (48 percent) sent through the correct information when replying to an email enquiry from a potential customer with 27 percent not responding at all.

"Providing quick, understandable answers to customer questions online will be fundamental to retail success this Christmas. Companies need to be clear, transparent and consistent with information - otherwise they risk losing vital Christmas sales as nervous customers shop elsewhere. The good news for retailers is that there is still time to update their websites before it is too late - but they need to hurry as Christmas is fast approaching," added Roche.

The news comes as Visa Europe predicts today (Monday November 28) will be the busiest online shopping day of the year. Dubbed Mega Monday, the credit and debit card firm expects £303 million to be spent online on Visa cards alone today, which erquates to £210,000 per minute or £3,500 per second.

Visa said more than 4.8 million transactions will be processed throughout the day, or around 3,300 per minute. 1pm will be the peak period as shopper log-on during the lunch break, closely followed by a rush which is expected to kick-off at 7pm.