"After several decades of implementation of this policy, an array of management problems associated with the burial grounds have emerged," Lai said in a written statement.

The problems were "complex and multi-faceted" involving five different departments: Home Affairs; Lands; Agriculture, Fisheries and Conservation; Food and Environmental Hygiene; and Water Supplies.

Under the policy, relatives of the deceased or their agents can apply to their local district offices for burial certificates if they undertake to observe requirements on land use, public health and environmental protection.

But activist Eddie Tse Sai-kit, who has also been tracking alleged burial-ground irregularities, said those requirements were rarely enforced, giving rise to abuses.

Tse, convenor of the Alliance for Concern over Columbarium Policy, said he believed that officials never verified whether the bodies were within the permitted area as he had seen some graves occupying private land.

He suspected that the burial privileges could also be "sold" to non-indigenous villagers - as the power to scrutinise the villager's identity rested on the village representatives.

"The government departments have been passing the buck and turning a blind eye to the problems," said Tse.

He added that even the sizes of the graves were not properly controlled, with some measuring up to 500 sq ft, and some sites were so overcrowded that it was difficult to walk between the graves.

The public can file written comments and provide information on the issue to the Ombudsman's office up until February 14.

A Home Affairs Department spokesman said there had been an average of 900 to 1,000 approved burials in each of the past five years.

A spokesman said the department would co-operate fully with the probe.