The Sri Lankan government says it is taking measures to ensure that the camps housing refugees will cope with the onset of monsoon rains.
UN agencies have expressed concern that the camps will flood, and the thousands of people in them will have no access to clean water.
The UK says it will soon withdraw all but emergency funding for the camps where about 250,000 displaced Tamils are confined in northern Sri Lanka.
The announcement came after the UK Development Minister Mike Foster visited the biggest camp at Menik Farm.
He said 70% of people should be able to leave and stay with host families.