Speaking at a international summit in central London to raise awareness about the outbreak in West Africa, William Pooley described attempting to help a boy also struck down with the illness.

"The boy had diarrhoea and he was very weak, too weak to get up," he said.

"I cleaned him up as best as I could with the limited materials available and removed his dirty clothes.

"The next morning I saw him lying as I'd left him on the bed and he wasn't breathing. His lips were drawn back, in a grimace, his eyes were vacant.

"I lifted his hand, just to confirm things, and his whole body turned rigid and cold. I put him in a body bag as his sister looked on."

Visibly emotional, Poole said he had significant concerns about the impact of the outbreak.

"My specific fear is that the horror and the misery of these deaths really fill a well of my despair and I just don't know what happens if that is repeated a million times," he said.

It came as British MPs warned international aid cuts for two of the world's poorest countries may have helped the spread of the deadly Ebola virus.

The claim was made in a scathing report from the Commons' international development committee ahead of the conference.

In the report, the British Department for International Development and the European Union are accused of doing nothing to deal with the fact that tens of billions of euros of EU-led health aid was not being passed on by Liberia's finance ministry.

"There is an alarming lack of capacity in the health system, including a shortage of skilled clinicians," the MPs said.

British International Development Secretary Justine Greening said: "The picture painted by Will Pooley of his experience and the children he had cared for but who nevertheless died gave us a real sense of what this disease is doing to families and to people on the ground."

The president of Sierra Leone, Ernest Bai Koroma, was due to attend but the chartered plane he was due to fly on "experienced significant technical difficulties prior to take off", according to the Foreign Office.

Experts say the outbreak has developed at an unprecedented scale and is in danger of spiralling out of control.

In Sierra Leone alone, an estimated 765 new cases were reported last week - a rate of five every hour - in a country where there are currently only 327 beds available for patients.

The conference comes as it emerged a Liberian man who is the first person to be diagnosed with Ebola in the US was initially turned away by hospital staff and had contact with five schoolchildren.

The man arrived in Texas from Liberia on 20 September to visit his family. He became unwell four days later but was not admitted to hospital until 28 September because of a mix-up.

He is now being treated at the Texas Health Presbyterian Hospital Dallas where he is said to be in a serious but stable condition.

Experts believe they have a 90-day window to halt the spread of Ebola, or 1.5 million people could be infected by January.

The death toll from the highly infectious virus, which has spread across Guinea, Liberia and Sierra Leone, has reportedly risen to more than 3,000.