The warning comes as Australia is in the grip of its worst season on record with more than 70,000 cases of flu and standing room only in some Accident and Emergency departments.
Specialists say this strain is likely to hit our shores this winter as global travel means the virus will “almost inevitably” be carried across.
Professor Robert Dingwall, a public health expert at Nottingham Trent University said the outbreak presents the most serious challenge since the 1968 flu pandemic which originated in Hong Kong and killed a million people worldwide.
Scientists are concerned about “virological drift” where flu evolves so that even if a vaccine works in one country, it may not be effective months later.
Prof Dingwall said: “Based on the Australian experience public health officials need to meet and urgently review emergency planning procedures. Public Health England should be working with local authorities and local health services to ensure more hospital beds are freed up. We need to be prepared, alert and flexible.
“There is no point in trying to close the borders. It’s almost inevitable this will come to us. This is potentially the worst winter since the Hong Kong flu outbreak of 1968. Lots of people have been very badly affected in Australia and whilst their mortality rates are not out yet we suspect this is a more severe strain than most other years.”
The warning follows a speech earlier this month from NHS chief Simon Stevens who said the NHS may not be able to cope with the pressure.
He told delegates at the NHS Expo conference in Manchester: “The signs from Australia and New Zealand are that it has been a heavy flu season and many of the hospitals down there have struggled to cope. I’m confident this is not just the biggest on record but the largest flu outbreak we’ve seen for some time.”
Professor John Oxford, the UK’s leading flu expert, said more effort was needed on vaccinations.
He added: “I would be very surprised if this virus doesn’t arrive in the UK from Australia. We cannot be complacent and I am very worried about increased mortality. We need to boost our vaccination programme.”
Professor Hugh Pennington, a leading expert in disease at the University of Aberdeen, said: “We have to assume a flu outbreak might reach epidemic proportions.
“We need to find out exactly what the virus is in Australia and if it is significantly different from our vaccine.
“If it is significantly different we need to produce something that will be a match and we need to ramp up the vaccine programme for those in high-risk groups such as elderly people.”
A spokeswoman for Public Health England said it was: “Continuing to prepare for all scenarios this winter and this includes the implementation of the vaccine programme.”
She added: “Our vaccines contain the strains which the World Health Organisation recommends we vaccinate against, based on the best available evidence.
“It takes six months with current egg-based technology to produce sufficient quantities of vaccine for the annual campaign.”