An Orchard Road shopping mall has not only banned construction workers from using its public toilets, but also threatened them with fines and expulsion if they disobey.

Wisma Atria has put up signs outside the men's toilets on five floors telling construction workers to use only the toilet in the carpark on the fifth level, behind the cargo lift.

The signs, printed on paper in English and Chinese, warn that those who flout the rule will be fined and "immediately banned" from working in the mall.

Full-time volunteer Hoh Jian Yang, 26, spotted the signs while shopping at the mall last Sunday. He told The Straits Times he felt the signs were discriminatory.

He said: "Denying certain classes of people access to public amenities encourages the view that they are, in some way, lesser human beings.

"That these amenities were almost certainly constructed by workers themselves adds a new layer of perverse irony."

A spokesman for YTL Starhill Global Reit, which manages Wisma, defended the signs, saying: "The restriction was to ensure that shoppers enjoy a conducive shopping environment within the mall."

He said the restriction arose because shoppers complained about the workers showering in the toilets or washing their tools in the sinks.

He added that the restrictions have been in place since Wisma's last major renovation in 2011. He declined to disclose the size of the fine levied or how many people have been penalised to date.

Construction workers The Straits Times spoke to at the mall said they had not noticed when the signs went up, mostly because they were aware of the restriction, so did not use the toilets anyway.

A 33-year-old Bangladeshi doing renovation work on the mall's fourth floor said: "Every morning at the safety briefing, they remind us not to use the downstairs toilets. Our shoes are dirty and the public doesn't like it."

An Indian national in his 30s said: "There is a CCTV outside the toilets and if they see us go in, the penalty is to my company. So we cannot do it."

Both men declined to be named as they feared reprisals against their employers.

While some workers said the carpark toilet was "okay for workers", others found it far from ideal. A 31-year-old Malaysian carpenter, who gave his name as Nicholas, said in Mandarin: "It is really very hot. There is only one tiny fan. Especially in the last week, when it was so humid, it was not very nice."

Singapore Contractors Association president Kenneth Loo said it was the mall owner's prerogative not to have workers using the same toilets as customers, but there might be a cost factor involved in sending them to a toilet not close by. "If the worker has to walk very far, then you lose productivity."

Advocates for migrant workers - who typically comprise a large proportion of construction workers - said a blanket ban might be going too far.

Transient Workers Count Too executive committee member Debbie Fordyce said workers should be advised against behaviour such as changing clothes openly or showering with the hose, but she did not think shopper complaints should have dictated an absolute ban.

"If the complaints are that they are making the floor dirty, they're not doing it because they're sloppier people. It's just the nature of their work. They were asked to work in that area and they have the same physical needs that other people do."

Said Mr Hoh: "They could just have easily have put up signs cautioning workers against showering or washing tools and told them to do it at the fifth floor toilet.

"Instead they decided that a policy of segregation was better. I feel it's a disproportionate response."