A total of 200,000 people could be infected if a new superbug - an infection that cannot be treated effectively with existing drugs - develops, according to The National Risk Register of Civil Emergencies.
The report also states that over the next twenty years the number of infections complicated by superbugs are expected to rise significantly.
It warns that routine surgery could become 'high-risk' because of the growing resistance to antibiotics.
The report, which assesses the threat level from emergencies and is produced annually to help the Government decide on policy, states:
"An increasingly serious issue is the development and spread of AMR (antimicrobial resistance), which occurs when drugs are no longer effective in treating infections caused by micro-organisms.
"Without effective antibiotics, even minor surgery and routine operations could become high-risk procedures, leading to increased duration of illness and ultimately premature mortality.
"Much of modern medicine (for example, organ transplantation, bowel surgery and some cancer treatments) may become unsafe due to the risk of infection.
"In addition, influenza pandemics would become more serious without effective treatments."
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The assessment continues: "The numbers of infections complicated by AMR are expected to increase markedly over the next 20 years.
"If a widespread outbreak were to occur, we could expect around 200,000 people to be affected by a bacterial blood infection that could not be treated effectively with existing drugs, and around 80,000 of these people might die.
"High numbers of deaths could also be expected from other forms of antimicrobial resistant infection."
Politicians and scientists have previously warned of the need to find a cure for infections that have become resistant to drugs, with David Cameron stating it was a 'very real and worrying threat' that could send medicine 'back into the dark ages'.
Last year a report from the World Health Organisation (WHO) stated that antibiotic resistance is no longer a looming danger but a reality with the potential to affect anyone of any age in any country.
Professor Dame Sally Davies, chief medical officer for England, said: "The world simply cannot afford not to take action to tackle the alarming rise in resistance to antibiotics and other antimicrobial drugs we are witnessing at the moment."