Customers and investors are waiting to see if the bank will be forced to pay compensation.

After delaying the report from the end of 2015, the Financial Conduct Authority (FCA) had previously said it would publish the report as soon as possible in 2016.

"We are in the latter stages of the review," FCA acting Chief Executive Tracey McDermott told parliament's Treasury Select Committee.

The FCA was scrutinising the draft final report from independent "skilled persons" into RBS's treatment of business customers in financial difficulty. McDermott said there will be discussions with the skilled persons and RBS before the report is published.

It has not yet been decided if all the findings of the skilled persons would be published alongside the main report, she added.

RBS has been accused of pushing viable firms into its so-called Global Restructuring Group so it could seize their assets and charge higher fees.

Lawmakers also grilled the FCA over how its new chief executive Andrew Bailey, was selected.

A panel interviewed several candidates, with McDermott and Australian securities regulator Greg Medcraft reaching the final stages. Ultimately, the decision was taken by Chancellor of the Exchequer George Osborne.

FCA Chairman John Griffith-Jones told lawmakers that after McDermott withdrew her candidacy, the selection panel was hesitant about wanting to put forward just one name.

Osborne then selected Bailey, currently Deputy Governor of the Bank of England, who was not formally interviewed by the panel, Griffith-Jones said.

Griffith-Jones said he did have informal talks with Bailey about the top job. Bailey is on the FCA board and is well known to staff and the selection panel.

"The overwhelming feeling in the building on the announcement of Andrew's appointment is one of excitement and approval," he added.

(Reporting by Huw Jones, editing by David Evans)

By Huw Jones