He said the success of the exercise would be difficult to assess because originally, the exercise was expected to be a final showdown between pan-democrats and Beijing allies.

But since no major government allies are taking part and the only opponents are relatively unknown candidates, the two parties will no longer set an official benchmark. They will only hope for the largest possible turnout.

The by-elections have been triggered by the resignations of five lawmakers - three from the league and two from the Civic Party. They are being viewed by the camp as a de facto referendum on the pace and scope of democracy.

Wong Yuk-man, the league's former chairman who has resigned from his Kowloon West seat and is running to regain it, said if 80 per cent of total votes went to the 10 pan-democrat candidates, the government would feel pressured.

'That's why we want one million voters to back the referendum for universal suffrage,' Wong said.

His colleague Albert Chan Wai-yip, who is running for the New Territories West seat he has resigned from, said it would be an 'unprecedented success' for pan-democrats if the turnout was higher than 25 per cent.

'If it passes the 30 per cent mark, it will be two slaps on the face for the communists,' he said.

The Civic Party said it hoped the turnout was as high as possible.

Originally, the league and the Civic Party said they would call the exercise a failure only if the total vote count their five candidates received was lower than their main pro-government opponents, with a condition that the turnout was higher than 50 per cent.

With Chief Executive Donald Tsang Yam-kuen yet to say whether he will be voting, and the general boycott by main government friendly parties which are calling on their members not to vote, the election atmosphere is at best lukewarm.

Yesterday, executive councillor Anthony Cheung Bing-leung said he has decided not to vote on Sunday, although he will be in Hong Kong over the weekend.

Independent lawmaker Lam Tai-fai said he would not be voting, and challenged the chief executive to clearly announce whether he intended to vote to minimise confusion.

At least four ministers - Financial Secretary John Tsang Chun-wah, Secretary for Food and Health Dr York Chow Yat-ngok, Secretary for Home Affairs Tsang Tak-sing and Secretary for Education Michael Suen Ming-yeung - will be on overseas trips.

Secretary for Transport and Housing Eva Cheng may leave Hong Kong for a visit to Beijing on Sunday, pending confirmation on the arrangement.

An official close to John Tsang said the financial secretary's visit to Heilongjiang and Vladivostok in Russia from Sunday to next Saturday had been planned more than six months ago, well before the date of the Legco by-elections was decided.

According to a survey by Lingnan University's public governance programme, the turnout for the by-elections will range from 11.9 per cent to 22.6 per cent.

The estimate came as 41.5 per cent of 1,094 respondents said they would vote on Sunday while 41.7 per cent said they would not, and 16.5 per cent said they had not made up their mind.

On their travels

Financial Secretary John Tsang Chun-wah leads a delegation to Heilongjiang province and Vladivostok in Russia from Sunday to next Saturday.

Secretary for Education Michael Suen Ming-yeung leads a higher education delegation to Malaysia and Indonesia on Sunday

Secretary for Home Affairs Tsang Tak-sing visits Hefei on Sunday

Secretary for Food and Health Dr York Chow Yat-ngok attends the World Health Assembly in Geneva on Monday