Documents released for public view show that Britain's foreign minister was advised to evacuate people from Kiribati and Tuvalu in the last years of the colonial administration.
It was suggested that the entire population of some islands could be resettled in other countries by 2025.
Ben Lowings reports from London.
"The views were expressed by John Smith, governor of what was then the Gilbert and Ellice Islands Colony. What he says is startling, for it suggests he had little interest in helping the locals maintain their traditional way of life. In hindsight however it appears prescient, given how the atolls are now threatened by the rising sea levels attributed to climate change - and the president of Kiribati has recently asked for help to resettle his people. In the mid-Seventies, John Smith was saying that I-Kiribati and Tuvaluans needed to move off the islands to work in a modern economy and maintain their standards of living. The alternative, he said, would be for the rest of the world to pay for the technology to keep the islanders at home."