Malaysian electoral watchdogs said yesterday there were major discrepancies in voter lists, including some two million people registered without addresses, warning the flaws could help the scandal-hit government at polls next week.

Prime Minister Najib Razak is facing a tough test at the Wednesday vote due to a corruption scandal surrounding state fund IMDB and a challenge from veteran ex-leader Mahathir Mohamad, 92.

About 15 million Malaysians are registered to vote, and analysts have warned the poll could be the dirtiest in the country's history as Najib seeks to ensure his Barisan Nasional (BN) coalition extends its six-decade hold on power.

Yap Swee Seng, executive director of electoral reform group Bersih, said there were 10 major irregularities in voter lists, claiming the flaws reflected the Election Commission's failure to ensure a clean and fair poll.