Doorstaff licensing body the Security Industry Authority (SIA) has been given an extra £17.4million of public money so it carry out its work.
The National Audit Office (NAO) said the cash is needed because the body has struggled to deal with licensing demand and systems to process applications.
Tim Burr, head of the NAO, said: "The security industry has been subject to suspicion and even criminality in the past and the SIA has done well to set up a licensing system which has secured a high level of compliance.
"Poor cost forecasting and ineffective management of the licensing scheme have, however, resulted in the SIA, spending over £17m more than planned.
"The authority needs to improve the quality of its forecasting and its management of the scheme so that it is better equipped for dealing with future demand for licences."
The shortfall in finances largely stemmed from the SIA originally charging £190 for a licence, but it costing £215 to process each application.
Since the SIA was set-up five years ago it has issued nearly 250,000 licences and there is a 90 per cent compliance rate among doorstaff.
Mike Wilson, SIA chief executive, said: "We welcome and accept the NAO's recommendations. Implementation of the report's recommendations is already being planned. "Indeed, in some areas, progress had already been made prior to the review, such as the feasibility study to consider the compulsory registration of private security companies.
"There will always be more to do, and we will continue to improve our regulatory regime and to raise standards in the private security industry to protect the public."