The Post Office is offering customers the option of sending packages using DPD and Evri.
For the first time in its 360-year history, the new service will allow customers to choose their parcel carriers over the counter in branches, in addition to existing services like Royal Mail.
It will begin in selected branches in time for the peak Christmas delivery season.
It comes after an Ofcom investigation into Royal Mail last year, after it failed to meet delivery targets during 2021-22.
At the time, the operator said it was “disappointed” with its performance, apologising to customers who were affected.
Although Royal Mail and the Post Office are separate companies, the two have a long-term agreement, with the former delivering letters and parcels and the latter offering postal services.
It means delays or disruptions at either, can directly affect the other.
Disruptions at Royal Mail continued into 2022-23, after it said the period was “one of the most challenging in our history”.
It said its services had been impacted by strikes and “high levels” of staff absence.
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An estimated 15.7 million people in the UK experienced postal delays in the month of May, according to research by the charity, Citizens Advice.
Neill O’Sullivan, managing director of parcels and mails at Post Office, said the choice of parcel carriers in stores will “meet changing customer preferences and the increasingly competitive market”.
“Our goal is to deliver unparalleled access to parcel services, addressing the needs of businesses and retail customers, both now and in the future,” he said.
In 2021, the Post Office began to offer Click and Collect services for both DPD and Amazon parcels, a response to the “rapid rise of online shopping”.