Tesco has apologised after its grocery website was overwhelmed with shoppers trying to book delivery slots for Christmas. Customers complained they had been forced to join an online queue for hours on Friday morning after Tesco opened bookings for Christmas week for shoppers who had signed up to the supermarket’s delivery subscription service. The retailer said it had also paused sign-ups to the “delivery saver” service “to help support our existing and vulnerable customers because of the high demand for online slots”. Messages on Tesco’s official Twitter account told shoppers the website had suffered from a “technical issue” that it was trying to fix. “We’re sorry if things take a bit longer than usual,” Tesco said. “We’re experiencing a huge volume of customers who are trying to book a slot at the moment.” It said it was “using a virtual waiting room to help us manage the flow”. It said the problems had been fixed by Friday afternoon. One shopper tweeted: “Over 2 hours of waiting now, been allowed in 3 times but each time it throws me out. I’m on the priority list for myself and also for my elderly neighbour. Help me out Tesco!!!!” Another wrote: “After almost a 90min queue all the slots I wanted were gone, I settled for something and then it crashes at checkout with a “oops something went wrong”. The problems on the website for the UK’s biggest supermarket are the first sign of the huge pressures for online delivery services expected in the run-up to Christmas as the November lockdown in England and fears of the virus keep shoppers away from actual stores. Supermarkets have dramatically ramped up their capacity to offer home deliveries, adding hundreds of thousands of new slots. Tesco alone has almost doubled its available delivery slots, to 1.2m a week, since the outbreak of the pandemic. Online grocery sales have jumped from 7% of overall sales to 13%. But availability is still expected to be tight in December. The online grocery specialist Ocado has said its Christmas slots are already booked but more might be made available in early December. Asda and Morrisons both started releasing delivery slots last week and both said they still had availability. However, Morrisons’ service on Amazon Prime, which includes unlimited fast deliveries, is limiting deliveries to one every four days because of high demand. Waitrose opened bookings more than a month ago and said some were still available. Sainsbury’s will gradually release its delivery slots from 29 November but those signed up to its delivery pass service can book theirs from 22 November.