The nation's largest parcel-delivery company, Evri, has issued an apology after continuing delays, with many not even receiving packages at all.
Evri told the BBC the backlogs should be cleared “over the next few days”.
However, one MP has called for them to be investigated.
Here’s what you need to do if your parcel is delayed or not delivered.
What to do if your parcel is delayed
Consumer law will protect you if you purchase something online and the item is damaged or never arrives.
The law, enforced by Trading Standards, allows you to complain to the retailer and seek redress from them.
All postal operators must have a simple and transparent complaints process in place.
Supermarket deliveries and the rise in online shopping means the demand on couriers is high.
It has recently been impacted by the holiday season and Royal Mail worker strikes.
“We continue to be impacted by high demand, staff shortages, and bad weather conditions,” said an Evri spokesperson, after pressure was placed on its service due to walkouts by Royal Mail staff in December.
Royal Mail staff have been striking over pay and unagreed changes to terms and conditions.
Negotiations are taking place between January 9 and 20, between International Distribution Services' Royal Mail and the Communication Workers Union (CWU) on their salary dispute.
Call for Evri to be investigated
During Prime Minister’s Questions on Wednesday (January 11), Labour MP Carolyn Harris questioned whether Evri should be looked into for “poor customer service and poor working conditions”.
The MP for Swansea East said: “Does the Prime Minister think that over 40,000 interactions via social media, email or letter relating to poor customer service and working conditions at delivery company Evri warrant an investigation by the relevant government department?
“His ministers in the BEIS (Department for Business, Energy, and Industrial Strategy) think no. But I am sure the Prime Minister would like the general public to believe that he is at least sufficiently interested in this issue to take action.”
Prime Minister Rishi Sunak then said: “I understand that other ministers in the government have addressed this issue and are currently examining the matter at hand. I would like to write to her when we learn more about the situation.”