'Unfairness is found in this government policy,' Lai said, urging the government to scrap the policy as a matter of fairness and consistency.

The Ombudsman's investigation targeted the so-called small houses - built on land granted to male indigenous villagers in the New Territories.

Although the Buildings Department received 2,400 complaints in the past four years about these buildings being illegal, it removed just 285 of them, or 13 per cent. In the same period, the Lands Department received complaints about 2,161 illegalities in small houses. But it only removed 118 of them, or 5 per cent.

The Ombudsman traced the poor results to a change of enforcement policy in 2002, which made a priority of enforcing work-in-progress infringements on small houses in the New Territories. In contrast, the usual priority in the urban area is to go after illegal structures up to 12 months after completion.

The inequality of policies between small houses and other buildings gave a signal that owners of small houses in the New Territories were 'privileged', the report stated.

Both departments were at fault, the Ombudsman said.

In one case, the Lands Department received a complaint about a swimming pool being built in a small house in November 2008. Department officials tried to enter the house four times in seven months but the occupant refused to let them in.

After five months, the complainant accused the department of mishandling the case and the matter was sent to the Buildings Department.

A Buildings Department officer entered the house and found the swimming pool, but did not take action to remove it, because the pool was completed - and no longer within the enforcement priorities.

Many similar case studies showed the work-in-progress policy 'clearly defies common sense and logic', the investigation report said.

Frank Li Wing-chi, the Ombudsman's chief investigation officer, said some small house owners used 'stalling tactics' - refusing government inspections during construction. 'The stalling tactics are fuelled by the lack of decisive action on the part of the administration,' Li said in the report.

Ombudsman Lai said the problem of illegalities among small houses has been worsening. In the past four years, the total number of complaints increased by 49 per cent, from 1,983 in 2007 to 2,997 in 2010.

Of the 9,608 complaints received in those four years, 2,400 were listed as work-in-progress cases that the Buildings Department should have followed. But the department took action only in 31 per cent of cases, and removed illegal structures 319 times.

Apart from swimming pools, infringements in New Territories small houses involved high walls, single-storey houses and kitchens.

The Development Bureau would not comment on the Ombudsman's recommendation the work-in-progress policy be scrapped. But it said 'there could be room for improvement in the enforcement strategy against unauthorised building work'. Members of rural affairs body the Heung Yee Kuk said they were unhappy with the Ombudsman's remarks about 'privileged' treatment.

Gripes on the rise

Complaints about illegal structures in the New Territories have increased this much in the past four years: 49%