The city's flagship Ponds Forge International Sports Centre - used by thousands of people including families and elite sports squads for major championships - has been beset by several alleged incidents in recent months which have sparked concern among visitors.
Then in May an investigation was launched after claims that a man was caught 'committing an obscene act' at the centre.
Now a parent of a child who uses the venue claims people have been taking drugs in a cafe toilet, a group of teenagers made threats to a visitor and homeless people are taking refuge there.
Bosses at Ponds Forge, which is operated by Sheffield International Venues, today accepted concern has been raised about a number of issues.
A spokesperson said a team of security staff have now been deployed on weekday evenings to "stop anyone from entering the venue if they have no real reason to be there."
He added: "You cannot just play the card that it is an open facility that anyone can use. Surely people's safety has to come first and the safeguarding of children."
He explained how one evening a few weeks ago he witnessed a man and woman aged in their 30s coming out of toilets in the cafe area with what appeared to be drugs paraphernalia in their hands.
On another occasion, he claims a parent of a child who was swimming asked a group of lads using the free wifi to be quiet.
But instead of lowering their tone they allegedly grouped around the parent, aged in his 60s, and began threatening him.
He added that many homeless people seek refuge in the cafe and also use the underground car park for shelter.
The security breach in which trespassers got into the pool area earlier this year was also highlighted as an example of poor safety measures.
At the time centre bosses said they would undergo a "thorough review of our building procedures."
And a few months later a probe was launched after claims a man committed an obscene act before running from the centre.
While centre bosses did not reveal the exact circumstances of the incident they did describe it as "exceptionally rare" and added that CCTV had been passed to police.
The concerned parent called for security guards and a turnstile to be installed at the main entrance.
Mandy Parker, Ponds Forge general manager, stressed today that customer safety is "of paramount importance" and added they had met with the parent to discuss their concerns.
She said: "The matters raised have been considered by our trustees in great detail and plans to improve the security at Ponds Forge are being assessed, with new measures already in place.
“As with many other large venues around Sheffield city centre, Ponds Forge has been attracting rough sleepers because of the severe weather we had during the winter."
She added the venue has been working closely with police officers and the Sheffield Street Rangers who conduct regular patrols to "move the rough sleepers from the area."
They are also due to ask the city centre policing team to add Ponds Forge to officers' regular patrol route.
In addition, external gates are being locked at night to prevent access to the car park.
She added: "We have increased staff patrols throughout the café, changing rooms and viewing balconies to ensure venue etiquette is adhered to.
“In addition, we are now part of the local Sheffield City Pubwatch Scheme, a volunteer group aimed at tackling crime and anti-social behaviour."
She said they are proud to have an "open-to-all" policy that retains a "strong sense of community" and added: "We work hard to keep all users safe and we will continue to collaborate with the relevant agencies to address the issues that are all too visible throughout our city.”