Enormous 'mutant' rats have reportedly made their way north from London and Birmingham to Liverpool.
The huge 'super rats' have been spotted across Merseyside, and are reportedly resistant to traditional poisonous bait.
Sean Whelan, of Whelan Pest Prevention, told the Liverpool Echo: "All around Merseyside there's been a problem.
"We're seeing bigger rats in Liverpool. They're super rats in my opinion."
The rodents are reportedly filling up on food left in bins near restaurants and houses.
Sean said: "Access to food is so easy for them. They're like humans, they eat and eat and get bigger and bigger."
According to the Daily Telegraph, a study from the University of Huddersfield in 2009 suggested that genetic mutations had produced a new breed of 'super rat' in Britain with DNA that was resistant to standard poison.
Pest controllers are now looking at a new, stronger type of poison to control the problem. But it would require permission from the Health and Safety Executive.
According to the Metro, Mr Whelan added: "They're becoming very resistant to bait in Liverpool.
"Soon we'll have to be putting third generation bait down which we will need to get legislation for."
Supersized rats started becoming more common last year. Adrian Whitaker came face to face with a huge rat in his Highgate home, and beat it to death with a chunk of firewood (pictured above).
There are around 80 million rats in Britain, which can carry diseases like Weil's disease, which can be passed on to humans.
Initially, it causes flu-like symptoms, but can lead to jaundice in the kidneys.