More cash should be spent on ensuring radio programmes meet editorial standards in the wake of the Sachsgate furore, a report into the aftermath of the scandal said today.
Although the independent review found "significant cultural changes" since the incident in October 2008, it said there is "little room for slack" in terms of staffing levels for compliance.
Lesley Douglas resigned as Radio 2 controller in the fallout from the on-air prank by Jonathan Ross and Russell Brand in which they left crude messages for actor Andrew Sachs.
It led to a shake-up in the way the BBC checks that programmes comply with editorial rules and standards.
The review published today said that the lessons from the incident "have been fully learned and much work has been undertaken to implement them".
It also found there was "stringent policing" of compliance in BBC production.
But it singled out BBC Radio 4 as one station where further investment is needed to keep on top of the workload.
"By virtue of the sheer volume of individual commissions, as well as the editorially and journalistically hard edge in much of the output, the demands made on executive production time are very considerable," the report said.
"We recommend that the compliance workload in Radio 4 should be reviewed and extra compliance resource should be allocated as appropriate."
It also said the BBC should look at its budgets and make more money available for appropriately qualified executive producers for shows made by independent firms.
The review - carried out by Tim Suter, formerly of Ofcom, and ex-chief executive of the Radio Authority - warns that increased pressure on BBC spending could divert resources to content rather than "overhead costs".
The authors say: "It is not the purpose of this report to argue the case for more resource spend on compliance staffing, but we wish to reflect what we have observed - which is that the system, as it is currently being operated, leaves little room for slack."
The review detailed how formal "risk lists" are now drawn up by the BBC. These identify all potentially problematic shows.
All "high risk" programmes are listened to prior to broadcast, and there are monthly "spot checks" on editorial compliance.
But the report said there was nothing to suggest that the increased attention to compliance has had an adverse effect on the shows which are commissioned.
"There is no evidence that programmes which ought to be made are not being made," the report concluded.