He later returned to his property on Peel Rise, The Peak, to lead a media pack to view the exposed unauthorised alterations. They include a 240 sq ft basement that Leung said 'existed when I bought the property in 2000'. The other illegal alterations discovered by buildings officials at Houses 4 and 5 at No4 Peel Rise include the main gate and a 40 sq ft single-storey structure. A parking space was also illegally covered.

Leung won the city's top job in March after his rival Henry Tang Ying-yen lost Beijing's support as his popularity plummeted when an illegal 2,250 sq ft basement was found in Tang's home in Kowloon Tong.

When asked whether the public would make a connection between the 240 sq ft basement and Tang's 'underground palace', he replied: 'Absolutely not; everyone can see it mustn't be that big.'

Tang was in Europe and not available for comment yesterday, but pan-democrats urged Leung to resign as his integrity was 'bankrupted'. Defeated pan-democratic candidate Albert Ho Chun-yan considered filing an election petition. Ho's Democratic Party has lodged a complaint with the Independent Commission Against Corruption alleging that Leung made false statements, possibly breaching the election laws.

The Buildings Department will issue an advisory letter to Leung about the structures.

After the media visit, Leung said it would take a few days to demolish the small structure and parking space cover. The gate could remain awaiting an additional application. But it could take two weeks to settle the problem with the basement, with options including filling up the space and other unspecified alternatives.

'The basement was unused before I won the election and has been undergoing painting works for police to stay overnight for security surveillance,' Leung said.

He added he discovered that about half of the 40 sq ft single-storey structure was illegal three months ago, but he stopped short of saying why he had not done anything about it in that time.

Contract workers had earlier demolished an illegal trellis with climbing plants, following the second Ming Pao report yesterday. On Wednesday afternoon, Leung dismantled a 100 sq ft glass enclosure in his garden, prompted by the first Ming Pao enquiry on Tuesday.

A veteran surveyor, Leung dismissed claims of deliberately hiding the illegal structures, saying 'I am a general practice surveyor, not a buildings surveyor. They are separate professions.'

Secretary for Development Carrie Lam Cheng Yuet-ngor - who is hotly tipped to be the next chief secretary - said she would not interfere with the investigation. 'As a politically accountable minister I will handle the issue in accordance with laws regardless of the social status and identity of the property owner,' Lam said.

Albert Ho urged Leung to resign on July 1 to allow a by-election.

'Hongkongers cast doubts on Tang's integrity following an illegal structure found in the basement at his property and we requested him to withdraw from the race,' he said. 'Employing the same standard, I can't see why Leung can stay on as the chief executive.'

Civic Party leader Alan Leong Kah-kit said he would request a special question-and-answer session in the Legco in July, so Leung could give his account of the controversy.

Labour Party chairman Lee Cheuk-yan said he was considering moving a vote of no confidence against Leung in the Legco.

Lawmaker Lau Kong-wah, of the Democratic Alliance for the Betterment and Progress of Hong Kong, who voted for Leung at the election, said the row was 'quite serious' and demanded an explanation. 'I don't understand why Leung did not consider his own situation when Tang was embattled in the illegal structure row at the campaign,' Lau said.

Lawmaker Jeffrey Lam Kin-fung, a core Tang supporter, said Leung should have been alerted last year when Chief Executive Donald Tsang Yam-kuen instructed his cabinet members to inspect their properties.

One of Leung's campaign advisers said the chief executive-elect had demolished an illegal structure in his property in Stanley as soon as he discovered it.