THE town's main library has shut its toilets for good after drug addicts left them in a disgusting state.
Library staff and visitors were regularly confronted with a mess and vandalism.
But when someone defecated in the middle of the floor it was the last straw and the council decided to close them permanently.
It is the latest effort by the council to control widespread anti-social behaviour in the town's libraries.
Council spokesman Richard Freeman said: "We had to close the toilets.
"Users left the toilets in a disgusting state. There was also a lot of vandalism.
"The situation in the library was completely unacceptable and they had to be closed.
"It is a well known fact that public toilets are often used by drug users."
People visiting the temporary library, in Princes Street, will be forced to go across the road to the council's Civic Offices if they need to use the loo.
And, with the new £9m central library in Regent Circus not due to open until next summer, the town's main reading rooms will be without any toilets until then.
Visitors had mixed feelings about being deprived of the toilets and some of them were not aware that they were locked for good.
David Howell, 32, of Walcot, said he had heard library users complaining to staff about the closure but he supports the measure.
He said: "I understand their decision to close them as the staff aren't trained to deal with drug users or security."
Kirsty Hicks, 18, from Wroughton, said: "I didn't think people would behave so badly in a library toilet. I think it is a bit extreme to shut them permanently, though. I thought they were just out of order."
Jamie Townsend, 22, also from Wroughton, said: "They should get a security guard as every place should have a restroom."
Insp Paul Hawkins, of Swindon police, said: "Often drug addicts are attracted to public toilet areas, including those situated in retail and commercial premises "But I am shocked to learn that they would stoop so low as to use the toilets of the town's library.
"The closure is going to be a great loss to the many genuine users of the establishment and I only hope we can resolve this issue before the new library is built."
Although the female and male toilets are permanently closed, disabled people are allowed to use the disabled toilet by requesting a key.
The temporary library building is part of the Paramount development, which refused to comment on the issue.
The borough's libraries face a constant battle to contain anti-social behaviour.
Assaults on library workers in the town have led to a number of Asbos being issued.
As reported in the Advertiser last month, police plan to set up a permanent base in Penhill library after staff were besieged by abusive youths as young as 10.
The council's library electronic service manager, Marion Stevens, told the Advertiser last month: "All our libraries have to cope with abuse week in and week out.
"It is a huge issue and staff are stressed by it."
Swindon Council says it has been forced to make security guards available and on call to vulnerable librarians during opening hours throughout the town.