The National Alliance for Autism Research has merged with US charity Autism Speaks.
The new international charity, to be called Autism Speaks, has set itself a ten-year target to achieve a breakthrough in identifying the causes of autism.
"What you have is an established research charity merging with an effective fundraising charity," said Hilary Gilfoy, chief executive of Autism Speaks UK.
The UK arm of the alliance was set up in 2004 as an affiliate of NAAR USA. The new charity aims to double investment in autism research.
"NAAR USA had been successful at persuading the US government to spend on autism research, and part of our remit here is to persuade the British government to do the same," said Gilfoy.