NatWest's service, called Fastpay, will handle payments of between £5 and £100, at a charge of 20p to send a transaction.
Despite the move, analysts have criticised banks for failing to develop a single method for electronic micro-payments.
Although micro-payment systems already exist, including those from online bank Egg and the US-based Paypal, Fastpay is the first such system in the UK from a high street bank allowing mobile phone payments.
After registering with the service customers will be able to make a payment to a company or individual by sending details of the payment to the recipient, who receives it in their own Fastpay account.
Duncan Brown, consulting director at analysts Ovum, said although it was good to see a high street bank offering micro payments the lack of standards could limit its adoption.
"Fastpay suffers from the same problems as the rest of these services - the recipient has to register with the service and they are not compatible with each other. Consumers may need many micro-payment accounts.
"There needs to be agreement between banks as there is with credit and debit cards if such payment methods are to be widely accepted," he said.