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Royal Mail is to trial a Sunday delivery service for parcels in response to the increasing demand for goods ordered online.

Later this summer it will open around 100 offices on a Sunday afternoon for customers to pick up their parcels.

Delivery offices with the highest parcel volumes across the UK will take part in the scheme.

The company will also try out parcel deliveries to addresses within the M25 motorway.

'Changing market'

"Through these new Sunday services we are exploring ways to improve our flexibility and provide more options for people to receive items they have ordered online," said Royal Mail's chief executive Moya Greene.

"The support of the Communication Workers Union (CWU) has enabled us to respond quickly to a changing market, " she added.

Media playback is unsupported on your device Media caption Royal Mail's Nick Landon explains the move

CWU deputy general secretary Dave Ward said: "Royal Mail's announcement about expanding delivery and collection services to seven-days-a-week is an exciting innovation which we welcome.

"We have worked closely with Royal Mail to develop how best we can go forward to grow the company together and improve the services for customers."

Royal Mail's express delivery service, Parcelforce Worldwide, which tends to deal with larger and more valuable parcels, will also offer a Sunday service to retailers from June. It will be up to the retailer to decide whether to offer it to customers.

The BBC's John Moylan says that rival firms, including Hermes and DPD, have already announced plans to deliver on Sundays and that some have been undercutting Royal Mail, which increased the price of posting letters and parcels earlier this year.

Royal Mail was privatised last year. The company reports its first annual results as a public company on Thursday.