Leung was referring to Tang's accusation that during a 'high-level meeting' in 2003 he had talked of using riot police and tear gas against demonstrators who were opposed to the introduction of national security legislation.

Tang also accused Leung on Friday of proposing to shorten Commercial Radio's licence renewal term, in an attempt to suppress free speech.

He said Leung had insisted on pushing ahead with the national security legislation even after half a million Hongkongers had marched against the controversial legislation.

Last night Tang said he had filed a report about Leung's 'libellous statements' to the Independent Commission Against Corruption. 'I also commissioned lawyers to write to Leung demanding him to retract his statements and [make] a public apology,' he said.

In Leung's opening remarks last night, he said he hoped to win the public's support through his vision and policy platform, but that he had been facing a smear campaign during the campaign.

'I even face character assassination by people adopting illegal and immoral methods,' he said.

He criticised Tang for making accusations without concrete evidence.

Public opinion polls declared Leung the winner again last night, as they did after Friday's debate. In a University of Hong Kong poll last night, 34 per cent of 711 respondents rated Leung as the best performer.

In one of the night's big surprises, pan-democratic candidate Albert Ho Chun-yan - who has virtually no chance of winning Sunday's election - nearly pipped Leung with a 32 per cent performance rating.

Tang, who was once seen as the front runner for the top job, came last, with just 15 per cent. Sunday's vote will be decided by the 1,193 members of the Election Committee.

Leung won a higher performance rating for Friday's debate, when he emerged the winner in an instant poll with 43.2 per cent, over Tang's last-place 13.4 per cent.

Tang was minster for commerce, industry and technology in 2003. He did not specify whether the 'high-level meetings' with Leung were Exco meetings, but Leung said he had only attended Exco meetings with Tang at that time.

Leung said on Saturday he was seeking legal advice on whether Tang had breached election rules by making false statements, saying he might lodge a complaint against his rival with the electoral office or sue Tang for defamation.

As expected, last night's debate, which was held at Kowloon Bay International Trade and Exhibition Centre, contained no bombshells like the one Tang dropped in Friday's contest.

Last night's match-up did not include a cross-fire section in which candidates could directly question each other.

Instead, questions were submitted by the public and by 13 members of the Election Committee. The three candidates also took questions from the public, and had a session for showcasing their policy platforms. Questions raised during the debate touched upon policy areas such as universal suffrage, education and health care.

Some internet users in Guangdong Province complained that the live broadcast of part of the debate was blocked and interrupted.