The "killer clown" craze has continued to spread across the UK with one force dealing with 14 reports in 24 hours.
Officers have been called to a string of incidents where pranksters or criminals dress as clowns trying to scare innocent bystanders.
Chief Superintendent Andy Boyd, of Thames Valley Police - whose force received the 14 calls - warned that the trend, which started in the United States, is a waste of police resources.
He said: "While we do not want to be accused of stopping people enjoying themselves, we would also ask those same people to think of the impact of their behaviour on others and themselves.
"In addition, their behaviour is causing multiple reports to our call takers and is tying up police resources which could impact on calls to other incidents."
His concerns were echoed by Chief Inspector Paul Staniforth from Gwent Police, which has now dealt with 18 reports including clowns "running through gardens and peering through windows, lurking around shopping centres, parks and schools and jumping from trees".
Terrified victims have taken to social media to document the encounters. Shaniece Price, 22, from Bloxwich, in Walsall, posted footage on Twitter of a red-haired clown who she claims tried to get into her car on Sunday.
Sporting Adidas tracksuit bottoms and a beanie hat, the clown can be seen running across the road towards the driver's door of her car.
She said: "He followed me to the pub. He pointed at me and gestured that he would slit my throat, stared at me for five minutes and then left."
In another incident, George Birkbeck said he spotted a sinister figure holding a hammer in a Tesco car park in Plymouth on Friday.
He brandished a beer bottle at the apparent prankster, seen wearing orange dungarees and make-up which mimicked Batman's 'Joker' character, who then ran off.
Elsewhere, in Norwich a 30-year-old man was arrested on suspicion of public order offences after allegedly dressing as a clown and jumping out on a woman in a park, screaming and then chasing her.
A string of other forces across Britain have dealt with reports in recent days of people dressed as clowns acting suspiciously and frightening members of the public.
A masked man carrying a knife left a group of children aged 11 and 12 "upset and distressed" when he jumped out on them on their way to the Hermitage Academy in Chester-le-Street, County Durham, at 8.40am on Friday.
A separate report saw two 12-year-old boys, one wearing a clown mask and another a V For Vendetta mask, go to Howletch Lane Primary School in Peterlee to try to scare children in the playground.
In Suffolk, a boy "younger than a teenager" was chased by "several people dressed as clowns" in Beatty Road, Sudbury, at 8pm on Thursday, Suffolk Police said.
Police in areas including South Wales, Gloucestershire, Bedfordshire, Essex and the North East have also dealt with a string of incidents.
Inspector Simon Starns, of Sussex Police, said: "We will respond if someone feels threatened and the culprit could end up being arrested and then they won't find it so funny."
On Sunday, Cumbria Police received nine reports from across the county of incidents involving clowns - one brandishing a knife and another a stick. Other incidents were reported in Whitehaven, Carlisle and Kendal.