Member of Parliament Antoninho Bianco has warned citizens that providing false information to receive more than one voting card is a criminal offence.
He said prosecution required a complaint to be made.
All people had a responsibility to report the electoral card fraud, he said.
He called for community leaders in particular to take charge and ensure the names of the deceased were taken off official databases.
Technical Secretariat for Electoral Administration (STAE) general director Aquilino Manuel Branco acknowledged that some people had multiple cards. Some offenders had been prosecuted by the Public Ministry, he said.
Branco said the problems arose because data was entered into the system manually, leaving it vulnerable to exploitation by people who registered more than once under different names and addresses.
Other fraudsters made false declarations that they had lost their cards in order to receive a second. Others are alleged to have misrepresented their age in order to receive the aged pension.
STAE was working to develop an online registration system but this was hindered by the lack of internet access in rural areas, Branco said.
He called for those who have multiple voting cards to surrender them to the STAE.
