A plague of 'super rats' could be swarming the UK by the end of the year as they become increasingly resistant to poison used by exterminators, experts are warning.
The alarm was raised after a series of reports from NHS hospitals, where rats which can pass on killer diseases were found on site near patients and around the grounds.
It is feared that the vermin could chew their way through the wiring of vital medical equipment, or even contaminate medical supplies with their droppings and urine.
The concerning reports have led exterminators across the UK to request they be granted stronger powers in their fight against the rats.
They claim if licensing authorities do not allow a new, far stronger poison to be used, 160m rats could be plaguing the country by Christmas as the vermin double in numbers - with some up to 2ft long.
An example of the growing problem was seen at Brighton and Sussex University Hospitals NHS Trust, where bosses have had to call in 72 visits from pest controllers between April last year and the end of March this year because of the issue.
A trust spokesman said: "It is extremely important that our hospitals remain clean and safe so we have a process in place to ensure any issues involving pests are dealt with quickly and humanely."
And a swarm of other disturbing discoveries have been made across the UK's hospitals and their surrounding grounds, including biting ants , cockroaches and bees nesting on site.
Experts believe the surge in discoveries of vermin come from rats growing resistant to the poisons used by exterminators - growing far bigger and stronger and building up an immunity.
Genetic testing by Huddersfield University has revealed that the rodents have developed a mutation that allows them to survive conventional poisons, while exterminators have continued to battle them using the same poisons since the 1950s.
Terrifyingly, researchers say the super rats could out-number humans two-to-one by next year across Britain.
However licencing authorities are hesitant because stronger rodent poisons could pose further risks to other wildlife, and also pets and even children.
But across the country, councils have reported a rise in the number of rats being reported, with Birmingham having the highest number of call-outs with 5,100 in the past year.
Andy Swinton, director of Swinton Pest and Property Solutions, said gamekeepers in the Scottish Borders found a huge rat twice the size of a normal one.
"The guy told me its head was the size of a cat's head," he said. "They called it a 'king rat'."
And poor pest control on farms and in city sewers, coupled with greater food waste such as unwanted potatoes, is leading to exterminators being swamped with emergency calls.
Reports of poison-resistant mutant rats were first made in the south of England in the 1990s and the problem has worsened in recent years.
Gavin Lindsay, owner of Anglo Scottish Pest Control, who recently caught a whopper measuring 18ins from nose to tail, said rats aren't being tackled properly in some areas.
It's feared many farmers, faced with rising costs and smaller profit margins, are cutting back on pest control bills.
Gavin said: "The population of rats is definitely increasing, especially in agricultural areas.
"But whereas we used to do 70% of our work on farms, nowadays it's only around 10%.
"A lot of farmers try to do it themselves but are not as successful. It's possible there are more of the bigger rats as a result.
"We see some whoppers on farms that are untreated."
Originally published on Mirror Online.