South Wales Police says "new and significant information came to light" which led to the case against John Clifton Davies to be dropped.
He has criticised the force for holding him for 16 months without bail, before finally speaking to key witnesses.
In 2010, South Wales Police launched an investigation into the death of 39-year-old Colette Davies which occurred in India in 2004.
Following a joint investigation with Himachal Pradesh State Police in Northern India and in consultation with the Crown Prosecution Service, a 50-year-old man was charged with her murder and fraud.
During the investigation which continued following the charge, new and significant information came to light which has been reviewed by the CPS.
As a result of this review it has now been decided that proceedings will be discontinued.
More top news
Food was found in a container, mixed with a substance believed to be rat poison, in a garden in the Roath area of the city.
Welsh sailor Alex Thomson is set to record a new world record for the greatest distance sailed solo in 24 hours.
Three teenagers and a 43-year-old man have been arrested on suspicion of murder and remain in custody.