Deaths from malaria in Africa risk soaring again if rich countries fail to sustain funding to combat the disease, the UK has warned.
International Development Minister Lynne Featherstone said a decade of aid that cut mortality rates on the continent by a third could "go to waste".
She urged other countries to sustain the effort as she announced an extension of UK help during a visit to one of the worst-affected nations.
Almost £40 million will pay for four million anti-mosquito bed nets and other help in the Democratic Republic of Congo (DRC), where she is marking World Malaria Day.
"The progress made in tackling malaria across the developing world over the past decade has not only saved over a million lives, it has helped reduce the economic damage that malaria can wreak on countries trying to grow their way out of poverty," she said.
"However, this progress is in danger. The international community needs to sustain its support to make sure the gains made over the past ten years do not go to waste. This must be matched by increased commitments from the governments of high-burden countries.
"The UK will not stand on the sidelines as millions suffer from this preventable and treatable disease. That's why we are stepping up our support for vital bed net and treatment programmes in the DRC, one of the worst-affected countries in the world."
The funding - which will also pay for work to reduce drug resistance and improve the capacity of the private sector to deliver therapies - is expected to protect six million people and save the lives of around 4,500 under-fives a year.
Malaria accounts for one in three deaths in the DRC - the second highest in the world - with under-fives exposed to an average six to ten episodes a year. Globally it kills 655,000 each year and makes 250 million severely ill. The disease is estimated to stunt economic growth in the most severely affected countries by 1.3% a year and the UK aims to halve the number of malaria deaths in at least 10 high-burden countries by 2015.
Up to £500 million a year of British aid is earmarked for malaria initiatives.