The Sri Lankan authorities have banned the adoption of children affected by the tsunami until further notice.
Some children are at risk following the disaster
The move follows concern expressed by the UN that some orphans were being targeted by criminal gangs.
There are no statistics in Sri Lanka for the number of children orphaned by the disaster. The government says it is compiling a census.
The government now says that 30,615 people were killed in the disaster. In addition, 4,356 are still missing.
"Adopting the children until a permanent solution is implemented is illegal," government spokesman Managala Samaraweera told reporters after a cabinet briefing.
"Not even a Sri Lankan can adopt a child affected by this disaster until the government has come out with their programme," he said. "Even if they are relatives, they are not expected to take children without government permission."
No reliable figures exist on numbers orphaned
The BBC's Elmo Fernando in Colombo says that the government has now made it virtually impossible to adopt tsunami affected children by requiring all would-be parents to get prior permission from the government before embarking on the normal legal procedures.
Thousands of children were forced to leave their homes during the tsunami, and there are fears that some of them may have been abducted.
"There are reported incidents," Lalith Weeratunga, secretary to Prime Minister Mahinda Rajapakse, told a news conference.
"If you look at the newspapers there are notices to find children who (witnesses) say have been snatched."
"There is a whole lot that needs to be done to ensure they are totally safe," he added, revealing that over 9,000 children had been affected by the disaster.
Meanwhile in India, a group of around 60 children's rights organisations have united to call for a year-long ban of adoptions of children affected by the tsunami.
They say that the measure would prevent traffickers from exploiting children orphaned in the disaster for cheap labour or the sex trade.
Such an initiative would also enable children comes to terms with their loss and allow time for counselling, they say.
It is argued that traumatised children need better protection
Campaigners say around 600 children were orphaned in the disaster.
"The Indian government should slap a ban on adoption from tsunami-affected coastal districts for at least a year," Sheelu Francis of the Tamil Nadu Women's Collective Training Centre told the AFP news agency.
"In the guise of adoption, human trafficking may happen. They make take this opportunity to snatch children for making them work in factories or homes or use them for the sex trade," she said.
But government officials argue that the issue of adoption needs to be treated with the utmost sensitivity, and that no decision has yet been taken on a ban on the adoption of children affected by the disaster.