Pay by Bank enables customers of UK businesses to make online payments for goods and services via their banking app, and directly from their bank account.

The app was developed by Zapp, a unit set up by VocaLink in 2013 with the aim of bringing real-time mobile payments - in store, online and through apps - to millions of Brits by integrating its system into bank apps and tapping into the Faster Payments rails.

The initiative signed up a host of big name retailers and banks ahead of a planned 2015 launch, vowing to win 20 million users by 2017, rivaling traditional payments giants such as Visa and MasterCard - which now owns Vocalink.

Yet Pay By Bank has so far failed to live up to the hype and is currently still only available to users of Barclays' Pingit app.

Mastercard sees Zapp as an important part of its Vocalink acquisition, giving it a new route into UK debit payments, currently a Visa stronghold.

Barclaycard's plans to extend the services to online merchant clients, and - by 2020 - introduce it as an embedded feature in its mobile banking app, is expected to boost the visibility of the app by adding both supply and demand simultaneously.

Darren Foulds, managing director of mobile payments at Barclays, says: “Consumers now want to pay quickly and securely in a variety of ways, whether that’s in person, online or on the go. By leveraging Barclays’ unique position as both an issuer and acquirer, our planned rollout of Pay by Bank app will simultaneously give customers and businesses more choice in how to make and take payments.”

The deal with Barclays follows recent integrations with PPRO Group and Worldpay, as Mastercard seeks to embed the option into merchant checkouts and at a growing number of Payment Service Providers.

Mark Barnett, divisional president of Mastercard in the UK, Ireland, Nordics & Baltics saysid: "The creation of the infrastructure for this new payment method is gathering pace and we look forward to maintaining this momentum as we bring it to market.”