The report by Rare Disease UK (RDUK) found that almost 20 per cent of sufferers lived with their conditions for more than five years before they received an accurate diagnosis and over 10 per cent had to wait more than a decade. Only 26 per cent of the 600 people questioned said they were diagnosed within three months of first noticing symptoms.
Rare diseases are classified as those which affect one in 2,000 people. RDUK says such conditions are "surprisingly common", with 3.5 million people in the UK experiencing one at some point in their lives.
Conditions include all childhood cancers, muscular dystrophy and Cockayne syndrome, characterised by poor growth and premature ageing.
Alastair Kent, chairman of RDUK, said: "Not only is it often a battle to get an accurate diagnosis, patients and families then struggle to find out the medical impact of a condition and how to manage it, on top of having to cope with day-to-day life without adequate support."