Aid groups have complained of delays getting aid to survivors
A Royal Fleet Auxiliary ship carrying aid supplies is to be sent to Haiti to help with the earthquake relief effort.
RFA Largs Bay will spend several weeks ferrying United Nations supplies.
The government has already pledged £20m to the relief operation, while public donations to a Disasters Emergency Committee fund have reached £31.5m.
Meanwhile, UK rescuers in Haiti have been redeployed to Petit Goave, west of the capital Port au Prince, which was hit by Wednesday's severe aftershock.
The firefighters will join German and Polish teams in searching for survivors of the magnitude 6.1 tremor, which struck eight days after the initial magnitude seven quake devastated the country.
Haitian officials say up to 200,000 people have been killed, 250,000 injured and 1.5 million left homeless.
Announcing the deployment of Largs Bay, International Development Secretary Douglas Alexander said: "This ship will provide a lifeline of essential supplies to sustain the recovery effort over the coming weeks to keep Haiti running.
The Disasters Emergency Committee is co-ordinating an appeal to help the people of Haiti
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"The focus until now has rightly been on the immediate task of trying to save lives but we must also plan for the future."
The ship is being sent at the request of the UN, and will be able to ferry supplies for the UN and non-governmental organisations (NGOs) involved in the aid effort.
Mr Alexander said: "Hundreds of thousands of people, many of them desperately poor to begin with, have been left with nothing.
"It will take many months for them to rebuild their lives and the international community stands ready to help."
Mr Alexander said the Royal Navy's professionalism and capability would "make a real difference".
Meanwhile, British Airways says a second relief craft will carry two Red Cross vehicles and 100 tonnes of food, blanket, tents and water supplies from Oxfam, the World Food Programme and Unicef to Haiti on Friday.
Brendan Gormley, chief executive of the Disasters Emergency Committee - an umbrella group of 13 major UK-based charities, said he was "stunned" by the British public's generosity.
"There is still a huge amount of work to be done," he said.
"However, vital aid is starting to get through in larger quantities, with some hospitals and clinics starting to receive life-saving medical supplies, food and water."
Aid has been slow to reach survivors since the first tremor on 12 January, leaving hundreds of thousands of people still without food or water.
Aid agencies, and some governments, have complained at delays in bringing in aircraft full of equipment.
The US military has defended its handling of the rescue operation at the airport, saying it was doing "everything in our power to speed aid to Haiti as fast as humanly possible".