Robust anti-fraud measures must be put in place before planning powers are handed over to district councils, the Northern Ireland Audit Office has warned.
Even though levels of corruption are low, Auditor General Kieran Donnelly said more must be done to reduce the potential for wrongdoing after 2015.
"Planning is one area within the public sector where there is a particularly high risk of fraud and corruption. It is not enough to establish controls to combat these risks," said Mr Donnelly.
With potential gains of up to £250,000 from fraudulent activity, the Auditor cautioned that there was a chance planning officials could be tempted to pocket bribes in return for speeding up the application process, approving applications or omitting costly planning conditions.
Another key risk is that employees or ex-employees could use their influence to affect planning decisions.
Mr Donnelly has called for the development of an anti-fraud culture.
"The Department must build a strong anti-fraud culture to ensure that these controls are implemented consistently.
"Robust counter-fraud arrangements must be in place before planning functions transfer to district councils in 2015," he added.
Planning transferred from local government to the Department of the Environment (DoE) in 1973. In April 1996 it became the Planning Service, an executive agency. As part of the preparations for planning and local government reform, planning functions reverted back to the Department in 2011 and are expected to transfer to the 11 new super councils by 2015.
The DoE has deemed the overall risk of fraud in planning as low, on the basis that internal controls were in place and few frauds have been detected.
However, the Audit Office described this assessment as optimistic given the inherent risks, particularly around planning decisions, cash handling and procurement.
"These controls undoubtedly help to manage the risk of fraud but given that no other part of the public sector is more open to the risk of conflicts of interest, bribery or corruption, in our view a low risk assessment is optimistic at best," his report added.
According to the Audit Office, internal controls and policies - including guidance on gifts and hospitality - are generic and take little or no account of the specific nature of the planning work and have to be tightened up.
Provisions for whistle-blowing must also be improved and given greater prominence on the DoE website.
Departmental managers should also be offered counter-fraud training.
The report noted: "Prior to the transfer of responsibilities to local councils, the current range of anti-fraud policies and strategies should be revised to reflect fully the risks inherent in the planning process.
"In addition, optimal training requirements for staff involved in dealing with fraud should be identified and a more targeted assurance programme should be developed, based on intelligence and a detailed assessment of fraud risks."