The Financial Conduct Authority has been given a deadline by MPs to publish a report into RBS's mistreatment of small businesses, with the watchdog's chief executive warned he risks "reputational damage" by holding up its release.
Following a grilling by the influential Treasury Select Committee, FCA chief executive Andrew Bailey was told by chair Nicky Morgan that he has until February 16 to release the report, or hand it over to the MPs.
Mrs Morgan said: "A version of the report is in the hands of third parties, it has been selectively reported by the media, and it may enter the public domain at any time.
"The FCA has lost control over the timing or content of further public disclosures from it.
"For these reasons, the Committee has requested that the FCA publish the final definitive version of the report, or send it to the Committee, by Friday 16 February."
It came after Mr Bailey's hours long grilling by the committee, in which the taxpayer-owned bank's shortcomings were again under the spotlight.
Mr Bailey was warned he risks making a "mockery" of the City watchdog if it continues to delay publication, with Stewart Hosie MP adding the hold-up risks "reputational damage" to the FCA.
"Time is important here. If you don't publish, others will," he said.
Mr Bailey said publishing the report without the legal checks sets a worrying "precedent" and he urged MPs not to do so using their Parliamentary privilege.
It comes after Labour's Clive Lewis revealed he has seen an unredacted copy of the report.
Mrs Morgan said there was "not time now" for the FCA to complete lengthy legal checks before publishing.
"There is an enormous desire for the report to be in the public domain," she said.
The FCA is also conducting a further investigation into RBS, which has been dogged by allegations that its restructuring arm GRG intentionally pushed small businesses towards failure in the hope of picking up their assets on the cheap.
Mr Bailey said the investigation is "well advanced" and "weeks" away from a conclusion.
He added: "We view the things that happened (at GRG) very seriously. I think it is very bad, very bad, shocking."
On the impact on RBS business customers, Mr Bailey told MPs: "People have suffered through no fault of their own.
"It's a terrible sadness and it should never have happened."
He added: "You can't have institutions that behave like this."