Ministers have been criticised for a lack of talks with their US counterparts over the risks posed by climate change to a key military base.
Foreign Office minister Sir Alan Duncan confirmed the UK has not "recently" discussed the impact on the Chagos Islands, also known as the British Indian Overseas Territory (BIOT), with officials from Donald Trump's administration.
Such a situation is "quite extraordinary" given the threat of flooding posed to the territory housing a major base for one of the UK's closest allies, according to Labour MP Bridget Phillipson.
In 1965, the UK bought the Chagos Islands, which includes Diego Garcia, for £3 million.
Chagossians were forced to leave the central Indian Ocean territory by 1973 to make way for the US military base on Diego Garcia, the largest of the islands.
This agreement with the US secured a discount on the Polaris nuclear weapons system for the UK, with the lease extended in 2016 by a further 20 years:
The expulsions are regarded as one of the most shameful parts of Britain's modern colonial history.
Ms Phillipson said the loss of coral reefs to global warming is a "particular issue" for the Chagos Islands, with Diego Garcia identified in 2012 as one of the top five most vulnerable military sites in the world.
She said: "Research by British scientists, published in November, points out that on Diego Garcia 'most of the land lies within a metre of the high tide level', that 'healthy corals are required to maintain growth rates of reefs that can match rates of sea level rise' and that 'in Diego Garcia the rate of (sea level) rise is higher than the oceanic average', and predicts that 'recurrences of mass (coral) mortalities will take place too frequently for any significant recovery of reef health in these atolls by the late 2020s'.
"It's now clear that without global action on climate change, an entire British overseas territory, housing a major base for one of our closest allies, is at risk of inundation, and yet we now know the Government hasn't spoken to the Americans about it recently.
"This is quite extraordinary."
Sir Alan, replying to a written parliamentary question from Ms Phillipson, said an assessment of climate change and its likely impact on the overseas territories, including the Chagos Islands, was commissioned in 2015 - with an inception report completed in October 2015.
He added: "Sea level rise and coastal erosion are considered to be the most significant potential climate change risks to BIOT. Climate change is a global concern.
"We will continue to closely monitor its effects on our overseas territories and take action where necessary. We have not recently discussed the effects of climate change on BIOT with US officials."