As many as 400,000 people are not listed at their correct address in Northern Ireland's electoral register, it has been revealed.
An estimated one in five of the entries are inaccurate, according to a report by the Electoral Commission.
It disclosed that the register was 71% complete and 78% accurate, compared with an assessment in 2008 when it was estimated to be 83% complete and 94% accurate.
The poll by an independent market research agency, which canvassed 1,500 addresses, suggested the processes employed by chief electoral officer Graham Shields to manage the register under continuous registration had not kept pace with either people moving home or people becoming newly eligible to join.
As a result there has been a significant decline in the quality of the register.
Anna Carragher, electoral commissioner for Northern Ireland, said she was now calling on the chief electoral officer, with Government support, to put in place an immediate action plan to address the findings.
The commission is an independent regulatory body set up by the Government. The survey was carried out between March and July.
She said: "We have important elections coming up over the next four years which will depend on complete and accurate electoral registers. Continuing with the status quo for managing the register is simply not an option."
Recommendations included a comprehensive action plan to begin early next year by the chief electoral officer to make contact with every household in Northern Ireland, to verify and update entries on the register and to identify new registrants.
Another recommendation was for a change in law to allow for a more flexible form of annual canvass whereby households as well as individuals can be asked to update their registration details.