Tesco's online slots for grocery deliveries from 12 December 24 December opened at 6am for customers who have paid for 'Delivery Saver' plans.
However, customers took to social media to complain that even though they had paid for priority access they found themselves in a queue behind thousands of other shoppers and when they did get to the front after waiting hours they were kicked off the site.
“Online Christmas slots are now available for Delivery Saver customers on our website and Groceries app after some customers temporarily had difficulty logging on or placing orders this morning," a Tesco spokesperson said.
"We're really sorry about that and it has now been resolved with slots available for both Home Delivery and Click+Collect over the Christmas period.”
Tesco has over 1.2 million slots available in the week leading up to Christmas.
Slots for customers without Delivery Saver plans open on 22 November.
On Monday, fashion retailer Primark's new click and collect online service crashed shortly after its launch, with some shoppers in Britain unable to access its website.