The Coalition government has activated a £2 million emergency plan to help tackle a cholera epidemic sweeping through Sierra Leone.
The Department for International Development (DfID) says it is using a network that includes private businesses and specialist aid organisations to deliver emergency medical, water and sanitation assistance to affected people in the west African country.
Close to 200 people have died and more than 12,000 have been infected by the water-borne disease, which causes severe vomiting and diarrhoea and can kill within hours if left untreated.
It is the first time the UK has used the network, called the Rapid Response Facility, since it was established in March.
Save the Children said aid agencies face a race against time to get preventative measures in place before the crisis reaches its expected peak in three weeks' time.
It said ten of Sierra Leone's 13 districts are affected by the disease and it is responding by assisting government treatment units, providing clean water to families and increasing the number of trained community health workers on the ground.
Save the Children, International Rescue Committee, Oxfam, Concern, Care International and the British Red Cross have been mobilised as part of the emergency response.
The DfID plans to help provide clean water and sanitation to nearly two million people as well as direct treatment for to up to 4,500 people affected by the disease.
Anti-cholera drugs and water purification kits will also be shipped to Sierra Leone.
DfID Secretary Andrew Mitchell said: "The cholera epidemic in Sierra Leone is fast becoming a crisis, with millions potentially at risk.
"The UK is - for the first time - activating the Rapid Response Facility, its network of private sector and aid experts to make sure we get aid to where it is needed, fast.
"Not only will our response be rapid, it will be efficient.
"We will monitor closely to make sure every penny of British aid achieves results and supports those in dire need.
"Urgent action is required to halt the spread of disease and save lives - Britain is leading the way."
The department's private sector partners will supply the majority of the aid organisations' relief supplies and logistics in the coming days.
Heather Kerr, Save the Children's country director for Sierra Leone, said: "If we can't get this outbreak under control quickly and comprehensively, it has the potential to kill many more children.
"Children die very quickly from cholera if they don't receive immediate medical help.
"The sheer volume of people who are contracting the disease means that aid agencies need more funding now to respond more efficiently to this devastating outbreak."
Cholera has spread quickly across West Africa, getting significantly worse in the last few weeks, with almost half those infected in Sierra Leone - the worst epidemic in the country for two decades.
The outbreak has been most severe in the capital, Freetown, which has a dangerous mix of poor sanitation, high population density and limited health services.