The state owned bank has hired former Bank of England deputy governor Sir Andrew Large and management consultant Oliver Wyman to conduct the review.
In May RBS said it had £20bn available to lend to SMEs but the bank’s lending to such customers fell by £452,000 in May.
Large said: “There is a disconnect between what the bank says it is doing on lending, and what many businesses say they experience on the ground.
"That is why we have been asked to conduct an independent review to establish what is going on, and what steps can be taken."
The bank said the review will attempt to find ways in which the bank could work harder to lend to businesses, such as relaxing criteria for first-time loan applicants.
Chris Sullivan, head of UK corporate banking at RBS, said: "Demand for lending remains a challenge, but we want to do more than just wait for demand to materialise.
"We want to play our part in securing the recovery."
A dedicated website will be set up for the duration of the inquiry through which small business customers can provide their perspectives and experiences on the group's lending.
The review's recommendations are to be published in the autumn.
