Mercury, a vaccine preservative, was withdrawn from childhood jabs five years ago after evidence linked it to brain damage.
However, the Sunday Express has discovered the pandemic vaccine, to be rolled out across the country within weeks, contains the heavy metal.
It also contains a chemical called squalene, used to stimulate the immune system to respond to the vaccine. Some scientists believe squalene is linked to autoimmune illnesses including multiple sclerosis, rheumatoid arthritis and lupus.
Squalene was included in the anthrax jab given to British and US soldiers during the 1991 Gulf War. Many claim it caused them permanent neurological damage, known as “Gulf War syndrome”.
Female soldiers given the vaccine were advised not to become pregnant for at least 18 months because of the risk of birth defects.
The swine flu vaccine could be given to more than 11million Britons in “at-risk” groups. These include asthmatics, heart patients and those with compromised immune systems.
But medical professionals and health campaigners are concerned about the risks of the cocktail of chemicals it contains.
Dr Richard Halvorsen, author of The Truth About Vaccines, said: “Mercury is one of the most toxic substances known to man. It should not have a place in any vaccine for anyone of any age.”
Jackie Fletcher, founder of Jabs, a group that campaigns to highlight the dangers of vaccines said: “Mercury is a known neurotoxin. Nobody knows what amount people can cope with – however small.” Last month the Sunday Express reported a link with a previous swine flu vaccine and a paralysis known as Guillain-Barre syndrome.