The company said it will be the biggest service of its kind, with post office branches opening longer so that goods ordered online can be collected.
Nick Landon, managing director of Royal Mail Parcels, said: "Royal Mail is a key partner for online retailers and we are well placed to benefit from the growth in e-retailing.
"The click and collect initiative will help online retailers give shoppers even greater control over the delivery of their items. We are committed to developing services to ensure we meet the changing demands of online retailers and their customers."
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