But Mr Yip said: 'I am doing no harm to the company and I'm not breaking the law. If they sue me, I'll see them in court.'

The dumping, which has been going on for a decade, illustrates the government's difficulty in controlling such actions because of loopholes in town planning laws.

The Hong Kong Institute of Education, a neighbour of the site, has filed complaints to the government about the dumping in its backyard for years, but to no avail.

During a visit to the site on Tuesday, trucks were seen dumping a mixture of soil and construction waste in heaps several metres high. Yesterday, dumping had stopped and the ground was being levelled.

The dump has expanded since 2004 from a narrow S-shaped strip in the centre of the valley, which is now used for a car park, garage and storage for construction materials.

Mr Yip said he planned to turn the site into a lavender nursery as a tourist spot.

'What I am dumping is good-quality soil, not waste,' he said, adding that the soil was excavated from a nearby construction site for a giant Kwun Yum statue.

Hundreds of trucks had dumped material on the site over the past two years, he said.

A Wheelock spokeswoman confirmed on Wednesday that the company held 50,000 square feet, or about 44 per cent, of the dumping area. But she denied leasing those lots to Mr Yip, although he was a tenant of adjacent lots also owned by the company.

She said the company had received complaints about the dumping earlier this month and since then had demanded that Mr Yip clear the site and erected signboards warning against dumping.

Although the site is zoned as a green belt, town planning officers have no power to take action as the site was not previously covered by a development permission area plan - a requirement for enforcement against land filling under the Town Planning Ordinance, and a legal loophole long criticised by green groups. The Lands Department also has no role as the old leases impose no restrictions on dumping.

Conservancy Association campaign manager Peter Li Siu-man said developers, who held a large amount of rural land as part of their land bank, should properly manage the lots to protect them against damage, although by law they did not have to. 'They should bear corporate social responsibility, as dumping is an eyesore and causes drainage problems,' he said.

Fencing the lots, installing closed-circuit television, and regular patrols were possible ways of protection, but as developers would build on the lots in the future, they often had no incentive to conserve them.

Complicating the issue is green groups' findings that some of the waste came from work sites at the Jockey Club racecourse in Sha Tin and the Hong Kong Sports Institute.

A spokeswoman for the Environmental Protection Department said it was investigating whether the case violated waste disposal laws and would launch legal action if there was sufficient evidence. After receiving complaints, it had urged the club and institute to remind contractors to dump waste properly, she said.