Argos has apologised to customers following complaints about how its new delivery service coped with Black Friday demand.
The shopping event came just under three months after the retail giant introduced its new Fast Track delivery service, allowing customers to order an item by 6pm and have it delivered by 10pm for a flat fee of £3.95.
The catalogue chain is not using courier companies and has instead directly employed 3,300 drivers, with a focus on customer service at the front door and the aim of using local people familiar with their own area to carry out the deliveries.
Argos was just one of a number of big-name UK retailers who struggled to cope with the volume of website traffic on Black Friday.
But customers have reacted with fury online after items ordered over the sales period failed to turn up.
Others have complained of lengthy waits on the retailer's customer service phone lines.
One Facebook user, Georgina Collins, wrote on the company's Facebook page that she was considering legal action.
She wrote: "So disappointed. Promised a delivery tonight after only 2/6 of my items arrived late with no confirmation.
"It's my daughters birthday tomorrow and it's now to late to do anything about it ... awful customer service ... hours and hours on hold.
"Will never use Argos again and am downhearted to have to get up in the morning and spend more hours on hold."
Nicky Crooks wrote: "Argos, guess what? My delivery didn't turn up again!!! That is two failed deliveries in two days, after you commented twice on here earlier today saying I would receive my item between 7 and 10pm tonight.
"What on earth is going on with your delivery services ... "
Lisa Toms posted: "I have been calling and waiting for over an hour every time trying to speak to someone about my order only to be hung up on or never actually speak to someone.
"I paid for a next day service and you can't even deliver two days later ... disgusting!
"Someone needs to explain where my order is ASAP. Black Friday is no excuse for poor service."
Argos said Black Friday was its biggest day ever for customers ordering via digital channels, with around 12 million overall web visits on the day and peak trading times seeing 18 transactions per second.
In a statement, it said: "On Black Friday our new Fast Track delivery services proved very popular and Argos had over 800 vans on the road who delivered tens of thousands of orders on Black Friday itself.
"The overwhelming majority of customers booking Fast Track same-day deliveries now are getting their orders successfully and the service is very much available.
"We apologise if any customer has experienced a problem with a home delivery and we are working through any individual cases as a priority.
"This is the busiest time of year for all retailers and despite our best efforts, occasionally we don't achieve the high standards we set ourselves and we are really sorry.
"We are also very sorry if any customer has tried to contact us unsuccessfully.
"We are putting extra people in to help answer calls and emails and extending our call centre opening hours to help us deal with customer enquiries.
"We will respond to every query as soon as we can."