Mercury, a vaccine preservative, was withdrawn from childhood jabs five years ago after evidence linked it to brain damage.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.