Mallzee, founded in 2013 to publish a flagship shopping app by the same name, has won a total of £2.5 million from RMG and some of its existing investors, including the Scottish Investment Bank, Par Equity and Skyscanner CEO Gareth Williams.

4J Studios co-founders Chris van der Kuyl and Paddy Burns also invested in the firm.

Royal Mail, as the largest single external shareholder, will be represented by Nick Landon, managing director of Royal Mail Parcels, on the start-up’s board of directors.

Mr Landon said: “I’m delighted to announce our investment in Mallzee.

“We think we can rapidly add significant value to the Mallzee business by introducing their solution to a wider audience, while the entrepreneurial and cutting edge mobile capabilities‎ that Mallzee have developed will complement our existing distribution services.”

He added that Royal Mail’s investment in Mallzee, together with its February acquisition of Storefeeder, demonstrated its “continued focus on digital innovation”.

Mallzee has more than 225,000 UK customers who use the app to browse over 100 fashion stores, including H&M and John Lewis. The app raises revenue through a commission on sales and by charging retailers to feature them.

Cally Russell, founder and chief executive of Mallzee, said: “With Royal Mail Group we have a partner that plays a vital part in the online shopping environment and one which is well positioned to enable us to access new retailers.

“Our existing angel investors and new backers such as Chris and Paddy have all scaled highly successful global businesses and their support and insight is going to be vital.”

Mr Russell also told The Herald that he wanted to grow the start-up’s staff in all areas.