Countries hit by last December's tsunami should allocate sufficient land to those made homeless, a charity says.
Thousands of people in Asia are still living in temporary shelters
Oxfam International says that, although thousands of homes have been built for survivors, new land must be provided.
It says many of those displaced have seen the sites of their former homes swallowed up by the ocean or lost by the imposition of coastal buffer zones.
Oxfam is supporting UN special envoy Bill Clinton's efforts to secure more homes in Sri Lanka and Indonesia.
The former US president is set to arrive in Sri Lanka on Tuesday.
The charity said thousands of homes had been built for tsunami survivors, but the governments of both countries were holding up progress because they had not drawn up policies to ensure appropriate land distribution.
The director of Oxfam, Barbara Stocking, said until new land is provided for those made landless the rebuilding process will be too slow.
"New land must be granted to those who lost it," she said.
"We're making some progress in individual cases, but we need these examples of best practice to be replicated right across the region."
Mr Clinton's visit was an appropriate moment to push for "this best practice to become the norm", she added.
The tsunami in the Indian Ocean on 26 December killed at least 200,000 people in countries as far apart as Indonesia, Thailand, Sri Lanka and Somalia.