Two members of staff at Bridgend council have been dismissed after an inquiry found irregularities in the running of the elections department.
Bridgend Council began its investigation in July 2005
A council investigation found £50,000 was improperly claimed in expenses and "numerous examples" of poor practice in the running of elections.
The expenses irregularities have been referred to police and the council said it would try to reclaim the money.
The inquiry began after a whistleblower came forward in July 2005.
According to the council's report, released on Tuesday, problems in the electoral services department's running of elections included discrepancies and inaccuracies in the election paperwork, in particular failures to follow the verification processes designed to safeguard results.
Elections affected included Welsh assembly elections in 2003, European, local government, town and community council elections in 2004 and the 2005 general election.
The report said election margins in the assembly election in 2003 and the general election were wide enough not to call the result into question.
But in 13 wards in 2004 local elections, the inaccuracies were deemed "unacceptable".
Discrepancies could have affected the results in three wards - Nottage, Ogmore Vale and Porthcawl East Central - according to the report.
However, under election law the results will now stand.
Bridgend Council also said claims were been made to the Welsh Assembly Government and the Department for Constitutional Affairs for election expenses in excess of the running costs and the residual amount shared out among electoral staff.
The council said £50,000 has been identified as improperly claimed and it would attempt to retrieve the money from the two council officers who have been dismissed, pending appeal.
Bridgend council said it first became aware of problems in the department when an internal whistleblower came forward in July last year.
The council's investigation was supported by the Electoral Commission.
Andrew Jolley, Bridgend Council's head of legal services, said: "The authority deeply regrets the unacceptably low standards of performance identified in the investigation.
"The council took the allegations, raised through its own whistle blowing policy, very seriously and acted upon them accordingly.
"The council is now ensuring that sound financial and procedural mechanisms are developed so as to restore public confidence in electoral services."