''This will be the dirtiest election ever because it is the most closely fought … Cheating and fraud could be the deciding factor,'' Ms Ambiga, who heads Bersih, a group campaigning for free and fair polling, said.

''There are many discrepancies appearing on electoral rolls, particularly with the sudden registering of foreigners, many of whom appear to be migrant workers.

''The mainstream media is far from free and fair … [The ruling parties] are doing everything they can to stay in power.''

Mahathir Mohamad, the former prime minister who ruled for 22 years, last week called for Ms Ambiga to be stripped of her citizenship.

Ms Ambiga said she and her family had lived in Malaysia for generations and she would leave it to others to judge whether Dr Mahathir - who broke a promise to stay out of politics when he left office in 2002 - was playing race politics in a country where ethnic Malays made up about 65 per cent of the population of 28 million. Ethnic Chinese account for another 25 per cent and ethnic Indians 8 per cent.

Opinion polls show the ruling Barisan Nasional (BN) coalition has lost much of the support of the Chinese, who have been alienated by corruption and policies favouring ethnic Malays, leaving the coalition heavily reliant on Malay votes to stay in power.

Ms Ambiga said voters had become empowered through the internet and social media and were no longer prepared to accept corruption.

''There is also for the first time a strong opposition which has brought out the scandals … I can sense the momentum is picking up,'' said Ms Ambiga, whose organisation has brought tens of thousands of people onto the streets to rally for free elections.

With only a few weeks remaining before the Prime Minister, Najib Razak, must call an election, religious tensions are also flaring over a call by an independent Muslim MP for the mass burning of Bibles which use the word ''Allah'' to refer to God.

Lim Guan Eng, the chief minister of the opposition-ruled island of Penang, put police on alert after a note was found at a church promising a Bible-burning ''festival'' this weekend. ''Let's teach 'em a lesson,'' the note read.

Financial markets are jittery over the political uncertainty in a country where the BN has never lost an election since independence from Britain in 1957.

At the last election in 2008, the BN lost its two-thirds majority as well as five out of 12 contested state governments.

Mr Najib, who became Prime Minister in 2009, has abolished repressive national security laws and hopes Malaysia's strong economic performance and handouts to poorer Malaysians will shore up his support.

In a bid to placate Malay voters, he has also softened an earlier pledge to replace a 40-year-old affirmative action policy that favours Malays with a ''new economic model''.

In one poll released in January, Mr Najib was only one percentage point ahead of the charismatic Anwar Ibrahim, a former deputy prime minister who heads the multi-ethnic opposition alliance Pakatan Rakyat (People's Pact).

An opposition rally drew close to 100,000 people in Kuala Lumpur on January 12, one of the country's largest-ever shows of political strength.

More than 3 million new voters have registered since the last election, deepening uncertainty about the result.

Analysts say many of them are young voters who are likely to be more open to change.

Seeking to appeal to these younger voters, Mr Najib's party lured the South Korean pop star Psy with a huge fee to perform at a Chinese New Year party in Penang on Monday.

Mr Najib promised to build 20,000 new houses and a new monorail system for the island before appearing on stage.

''Are you ready for Psy?'' he yelled to the fans, who yelled back, ''Yes''. But when Mr Najib then yelled ''Are you ready for the BN?'' many yelled, ''No''.

Ms Ambiga said her organisation is mobilising squads of citizen observers to fan out across the country to observe the election, which must be held before the end of June.

Requests to admit observers representing the United Nations or Western countries have been denied, although some local non-governmental organisations will be invited to polling stations, with restricted access.

''People have decided to take it upon themselves to observe the elections,'' Ms Ambiga said, adding she believes the election is too close to call.

''Malaysians have a habit of surprising - watch this space.''