The British Navy will send the aircraft carrier HMS Illustrious to help with the relief effort following Typhoon Haiyan, which hit the Philippines last week.
David Cameron announced the news during a visit to India, and added that the UK had given more than £20m in aid. The Prime Minister said that the ship will replace HMS Daring, which has already been deployed to the 7,000-island nation.
The storm killed least 2,300 people and displaced more than half a million.
The Illustrious is currently in the Gulf and is expected to arrive in the Philippines on 24 November.
Its helicopters may be used to assist with the distribution of food and water to survivors stranded in remote locations, and its facilities to make water drinkable are likely to be in demand in a country where supplies have been badly disrupted by the typhoon.
Mr Cameron said: "What happened in the Philippines is an absolute tragedy.
"You can see the devastation, the suffering, and it's quite clear that we are going to need long-term help for those people."