Rats are invading homes through toilets, with one woman left in shock after spotting a rodent below her when she was using the bathroom.
Andrew Dellbridge, head of Ace Pest Control, said rats in Norwich are getting 'bigger and braver', forcing one couple in the city to leave their home.
He said another customer was left speechless when she used her bathroom, heard a noise and then saw a rat in the toilet bowl below her.
Mr Dellbridge said the terrifying episode is becoming increasingly common and he has spotted rats 'as big as cats' in the city.
He told the Norwich Evening News: "I was called out to one job in Norwich and the customer could barely speak, she was in so much shock.
"She'd been using the bathroom and heard a noise. She looked down and it was in the toilet bowl. And this is happening more and more frequently."
"They used to work around us but now they're gaining access they wouldn't have attempted before."
Mr Dellbridge added that the issue is becoming worse due to overflowing bins and wild verges being filled with rubbish.
The pest control boss has been working flat-out through the summer, despite the winter usually being his busiest time of the year.
He said cats are no longer a solution to a vermin problem as 'a sensible cat doesn't like a big rat'.
It comes after huge rats ran riot in lockdown Britain - with easy access to food meaning the vermin grew in size and number.
Footage showed a pair of them - the size of a small cat - stealing food from hungry birds.
The plump animals climbed up the frame before gorging themselves on the food.
The large rodents were scampering around in broad daylight in full view of a family in Accrington, Lancs.
Experts said the easy access to food - with many businesses closed during the pandemic - caused the UK's rat population to skyrocket.
The number of rats increased from 120 million to 150 million during 2020, according to pest control company pest.co.uk.
The big freeze, lockdowns and food stockpiling created the ideal environment for rats and mice to enjoy a little quiet time in vacant buildings.
A rat's bite is in fact six times stronger, relative to their size, than a great white shark, pest expert Jenny Rathbone said.
Pest controllers have seen evidence of cunning rats moving a crisp packet and placing it over a glue trap, to enable them to travel across it without being caught.