That’s the terrifying doomsday warning from pest control experts who may just have a vested interest in not seeing their budgets further slashed by local authorities.

An increasing number of huge mutant rats – some up to 18 inches long – have been spotted across the UK in recent years thanks to the abundance of food strewn around by litter louts who dump their pizza and burger leftovers on the streets. Dash it all, one outsize middle-class rodent was even spotted recently in London’s fashionable Belsize Park.

Yet pest control budgets have been slashed by a quarter, with 200 local authorities in England spending 24.4 per cent less on average since 2010. There has also been a 16 per cent cut in the amount spent on street cleaning.

The British Pest Control Association warns that rat numbers are rising by about 15 per cent a year, driven by the ready availability of food.

And John McNeice, director of Scottish Pest Control Services, told the Daily Mail: “We see big rats in cold stores. The rats grow a very thick fur. That can make them look bigger. You might see a rat under a pallet that looks as big as a cat.”

The Mail reports that genetic testing carried out at Huddersfield University has indicated that some rats have developed a mutation that allows them to survive conventional poisons. As a result, some pest controllers want stronger poisons to be allowed.

Meanwhile, in other rodent-related news, scientists in Norway have announced that black rats may have been wrongly blamed for spreading the bubonic plague, which killed millions of people across Europe from the mid-14th century. They now believe that GERBILS from Asia may have been responsible for the deadly epidemics of the Black Death.

“If we’re right, we’ll have to rewrite that part of history,” said Professor Nils Christian Stenseth, of the University of Oslo, as reported by the BBC.

Gerbilieve it? We smell a rat…