British actress Emma Thompson has accused Western governments of "psychotic detachment" over their "failure" to fund the fights against Aids, TB and malaria.
Thompons said her daughter had inspired her to campaign
Thompson, an ambassador for UK charity ActionAid, said the Aids virus in particular was "the greatest threat to human existence in our history".
Thompson, 44, was speaking in London at the launch of the charity's latest fund-raising drive to find cures for the three diseases.
If they don't back it up with action then I simply can't believe what the politicians are saying
She said: "Why in this world do we find money for war when we are faced with the Aids virus - the greatest threat to human existence in our history?
"Why is it possible for our governments to exhibit what I describe as psychotic detachment? It is extraordinary that all this is going on and we have not done anything."
The film star said she had travelled to Uganda last year with ActionAid and seen first-hand how devastating Aids was in Africa.
She also urged people to write to their MPs and to join campaign groups to try and raise funding.
She was also angry the Global Fund set out to combat the disease was $1bn (£625m) short of its budget.
"It is absolute madness that we have allowed this to continue. What we lack is the political will. If they don't back it up with action then I simply can't believe what the politicians are saying."
Thompson said part of the reason for her involvement was her three-year-old daughter Gaia.
"I have a three-and-a-half year old daughter and I am here because I don't want to have to say to her that in the face of the greatest disease ever to hit the human race, I did nothing," she said.
The Oscar-winning actress is best known for her roles in films such as Sense and Sensibility and Howards End.
She is due to appear in the forthcoming Richard Curtis comedy Love Actually, which also stars Liam Neeson, Colin Firth and Rowan Atkinson.