The integrity of Malaysia's elections is in doubt because indelible ink meant to prevent fraud is easily washed off, according to the opposition and clean-polls activists.
The country's Barisan Nasional (National Front) coalition government bowed to pressure from mass rallies for fair polls and introduced the ink in the run-up to Sunday's general elections.
Reports have mounted that security personnel who took part in early voting had easily been able to clean off the ink, applied to a person's finger to show they had voted and which was supposed to remain visible for at least a week.
About 13.3 million Malaysians are eligible to cast ballots to fill 222 parliamentary seats and elect legislators for 12 state legislatures.
Lim Kit Siang, a veteran opposition politician, said on Wednesday that the Election Commission should immediately address the problem.
"Otherwise it will be a black mark on the commission and undermine the public confidence in the results," Lim said.
"The whole integrity of the electoral process has come into question."
However, Tan Sri Abdul Aziz Mohd Yusof, the election committee chairman, insisted that the ink could not be washed off.
Even if the stain on the fingernail could be rubbed off, the stain would stay visible on the skin surrounding the nail for seven days, he told the Malaysian Insider newspaper.
Barisan has ruled since independence from Britain in 1957, and Sunday's vote will be the first in history in which the opposition has a chance of winning power.
It will pit Prime Minister Najib Razak's Barisan coalition against Anwar Ibrahim's Pakatan Rayat (People's Alliance), which has pledged to tackle what it considers deep-rooted problems like corruption and racial discrimination.
Najib has repeatedly voiced confidence that his coalition would win and potentially regain a two-thirds parliamentary majority that it lost in 2008.
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Barisan's grip on power has weakened in recent years amid complaints about a lack of government transparency and racial discrimination.
Anwar told the Associated Press news agency on Tuesday that his alliance believed it could secure a comfortable majority, partly because of rising support among younger voters with an appetite for political change.
"People have enough of this semi-authoritarian rule, of complete control of the media, of strong arrogance, of power and endemic corruption," Anwar said in reference to the current government's control.
He also reiterated the opposition's concerns that Barisan would resort to electoral fraud to retain power.
The government has denied accusations that it planned to tamper with votes. It has sought to bolster its popularity in recent months by providing cash handouts to low-income households and offering other financial incentives.
Anwar, a former deputy prime minister who was fired in 1998 and jailed on sodomy and corruption charges that he said were fabricated by his political enemies, told Reuters he would step down if his three-party alliance fails to wrest power from Barisan.