Mr Zainal Sapari, the director for NTUC's Unit for Contract and Casual Workers, said he was concerned about cleaners sleeping in public places.
The majority of members from the unit are from the cleaning, landscaping and security sectors.
Mr Zainal, who is also the Member of Parliament for Pasir Ris-Punggol GRC, said that most cleaners should receive transport allowance.
He added: "Cleaners who work for the town council usually reside within the estate.
"Companies have a duty to provide accommodation for foreign workers but I do not rule out the possibility that the cleaners might find alternatives because they find their accommodation to be overcrowded."
Ms Sharon Kee, project director of Horsburgh Engineering, a company that supplies cleaners to hawker centres and offices, was surprised to hear that cleaners spend the night outdoors.
"It depends on the scope of work. Some of them can only start cleaning after operation hours. But even so, there is still public transport available if they work till 11pm," she said.
Mr Zainal has been fighting to raise the wages of those in the cleaning industry but it has been tough as companies try to seal a contract with a lower bid.
According to a report by The Straits Times, wages form about 80 per cent of a cleaning company's costs.
So raising their income would be tough.
Mr Zainal had argued that to raise wages for the cleaners, those engaging cleaning companies must be willing to pay more.
For a start, the Government sector is now only awarding contracts to accredited cleaning firms with the progressive wage model which sets out career ladders and pay benchmarks in low-wage sectors.
From next year, all cleaning companies need to follow these benchmarks to get licensed.
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