Roy Graham, aged 78, took pictures of the man who pulled down his trousers and squatted to relieve himself in the alleyway by the side of Lloyds Bank, off Pride Hill, in Shrewsbury.
One of the pictures taken shows the man's face and West Mercia Police say it will help officers identify the offender.
Widower Mr Graham downsized and moved to the town centre from Radbrook 18 months ago and he says although he loves the town centre life, Shrewsbury has been "going downhill" in that time. And he called on the authorities to take action.
Mr Graham's concerns come as police released grainy CCTV pictures from Claremont Hill where officers say there have been "numerous incidents of activities such as drug taking, urinating and littering in the area."
This is added to a pattern of behaviour from offenders who have been causing problems in Princess Street.
Mr Graham said passers by were aghast to see the scruffy man pull his trousers down, revealing his bare buttocks and relieve himself.
"He must have been drugged or drunk," he said. "I blame drugs for the deterioration in behaviour."
"The police are definitely not doing anything about it," said Mr Graham, whose claim has been countered by officers in the town.
He added: "I am horrified at the way this town has gone in the last few months. These people have been coming into Shrewsbury from outside of town and gathering at the top of Pride Hill.
"I can't believe the wokeness of the local police in not dealing with it."
Mr Graham added that he believes that "no place is perfect" but he has also seen a deterioration with litter and cardboard strewn in the streets.
"I used to feel sorry for them and would give them a pound or a fiver but am told that if you want to help them you should offer to buy them a sandwich," he said.
He fears that antisocial behaviour in the town will hit tourism.
"A couple from America were asked what they thought of the town and whether they enjoyed it," said Mr Graham.
"They said, 'We can't get out of here quickly enough'.
"It's terrible," he added. "I confronted one of them who was effing and c-ing in Pride Hill, and a lady winced. I'm old fashioned and don't like swearing in front of ladies. I told him to watch his language and he stared at me for a while. He did say sorry though.
"I think it does need confronting and I can't stand and watch but my son said I should be worried because they carry knives."
Police say they are continually patrolling in the area and review any evidence supplied.
Sergeant Gary Lansdale, of the Shrewsbury Safer Neighbourhood Team said officers "will take the appropriate action against those committing these offences"
He said such incidents have been going on for quite some time and include reports of people engaging in sexual activity, relieving themselves and drug taking.
Sgt Lansdale said: “These incidents have been going on for quite some time and have been addressed by encouraging residents and members of the public to report any incidents via 101 or contact us.
"There has also been lighting and CCTV installed where the majority of offences have been taking place.
"This location is a busy thoroughfare of the town and there are numerous incidents throughout the day but more of an increase in the evening on an almost daily basis.
"People have used the alley leading to residential properties as a public toilet, commonly urinating in the passageways or up against properties.
"There has been evidence of drug taking and drug dealing where paraphernalia such as needles have been discarded on the floor and leading up to people’s property, as well as reports of people engaging in sexual activity.
“Shrewsbury SNT are continually patrolling this area and reviewing any evidence that is supplied to us where we will take the appropriate action against those committing these offences.”
Councillor Richard Marshall, cabinet member for highways and regulatory services at Shropshire Council said the local authority is aware of the concerns raised by residents and business owners in Shrewsbury town centre.
"Since being made aware of the alleged anti-social behaviour, our rough sleeper team has completed a number of outreach visits and is ensuring those sleeping rough in the area are given the support they require to move on," he said.
"The team work in partnership with Shrewsbury Ark and the new drug and alcohol team, Reset, to offer advice and support for rough sleepers.
"Shropshire Council is working closely with local police regarding the alleged anti-social behaviour and is also liaising with businesses to address this.
"Rough sleeping is the most visible form of homelessness and we are committed to reducing the number of people having to sleep out to zero. Since November 2022 the estimated number of people sleeping rough in Shropshire has dropped from 16 to five.
"We recognise that often people are assumed to be rough sleeping when they do in fact have somewhere to return to and we are committed to resolving this behaviour also."
He added that the council has recently consulted on renewing a protection order for Shrewsbury’s town centre – and is looking to include other prohibitions.
"The Shrewsbury Town Centre Public Spaces Protection Order (PSPO) was brought in back in 2017 as part of an effort to tackle increasing public concern over issues of anti-social behaviour in the town centre," he said.
"The order specifically targets people leaving personal belongings out, drinking alcohol and urinating or defecating and gives police the power to move people out of the town centre for 48 hours. The findings of the consultation will form part of a report which we aim to bring to Shropshire Council’s cabinet in July.
"We urge anyone who witnesses or experiences any anti-social behaviour to call West Mercia Police on 101 which is available 24/7."