Royal Bank of Scotland and NatWest customers who forget or lose their cards can now withdraw money from ATMs using their mobile banking app.
Customers are presented with a 'GetCash' option within the RBS and Natwest iOS, Android and BlackBerry apps that lets them request up to £100.
A six digit PIN is then generated which can be entered at the banks' ATMs at any point within the next three hours to collect the money. Customers can make as many requests as they want in a day as long as they do not exceed their withdrawal limit.
RBS and NatWest already operate an emergency cash service which nearly 60,000 people have used this year. They are now extending the availability of the service to the 2.4 million customers who have the RBS and NatWest banking app on their phone, pitching it not just as a last resort in an emergency but an option for people who want to get cash to others or leave their wallets at home.
Ben Green, head, mobile, NatWest and RBS, says: "We've heard countless stories from customers who've left their wallet behind, or parents who need a quick way to send money across to their children immediately - GetCash means these problems have been solved in a totally secure and painless way."
The move to cardless ATM withdrawals is gathering pace: earlier this week manufacturer NCR unveiled its own system that sees customers initiate transactions through their mobile phones and then scan 2D barcodes on the machines' screens to get their cash.
Meanwhile, the RBS Group has begun letting customers donate to charity through its 8000 ATMs and cash deposit machines. Users can choose to donate amounts between £1 and £150 to charities including Cancer Research UK and Oxfam.
The move is part of a wider initiative involving the Link ATM network, with banks, building societies and cash machine operators agreeing to roll out the feature following a government green paper recommendation.