With the housing problems faced by single parents in the news lately, there has been a well-intentioned call for us to "forget HDB" and for civil society to step up ("Forget HDB. Time for civil society to step up to help single mums with housing", Chua Mui Hoong, The Straits Times Online, May 27).

Ms Chua's suggestion came in the wake of a report that an unmarried mother had adopted her own biological daughter in the hope that she could qualify for subsidised public housing. The Government then said that such a family set-up would not qualify. Citing the case, Ms Chua argued that it was time to go beyond lobbying the state, and urged civil society and individuals to offer direct assistance instead.

While there are important roles for civil society, the argument that we should count on civil society to provide housing solutions instead of pursuing policy change reflects a misunderstanding about the nature of housing problems, how public policies work, and what civil society can and cannot do.

In separate research projects we have conducted in recent years, we have learnt that single parents - usually single mothers - face numerous barriers when it comes to securing housing.

Unmarried parents and their children are not considered a "family nucleus" and thus, are not eligible to purchase HDB flats. Divorcees who are required to sell their matrimonial flats have to wait three years before they can purchase another subsidised flat. The income ceiling for HDB rental flats, at $1,500, is very low - well below the market rate of rental flats - and so some single parents have an income that is too high to qualify for HDB rental flats, but too low to afford open market rentals.

The result is housing insecurity and poor living conditions. Some families are forced to move from place to place, staying with relatives or friends for a short period each time, before they become an inconvenience and need to move on again. Some parents live separately from their children because it is difficult to find friends or relatives who can take in the whole family. Living conditions tend to be poor as host families have space constraints, creating tensions. Securing a roof over one's head can therefore lead to long-term deterioration of familial or friendship ties.

As we all know, a stable living environment is a precondition to well-being. To live dignified lives, each of us requires some space to call our own. Being able to go back to this safe space at the end of a day is a basic need.

For single parents, the economic and emotional stresses of being both wage-earners and caregivers are already high. The lack of secure and stable housing intensifies their hardship. The search for stable housing takes up immense energy and, in its absence, becomes a high priority in life. Unstable housing is especially distressing for kids. They may have to change schools, losing friends and trusted teachers. This can create discord between parents and their children.

Once we understand the costs of housing insecurity, it becomes clear that suggestions for people to open up their homes to single-parent families for short stays, in the style of Airbnb, will not solve the problem, as it is neither stable nor sustainable.

Policy solutions have important practical advantages over charitable initiatives: chiefly, scale and sustainability. Big-hearted individuals might help single-parent families one at a time but, on their own, their efforts will not be enough.

People "fall through the cracks", even with concerted state efforts; it is unrealistic and unreasonable to expect individual initiatives to address the needs of all.

More importantly, policies represent collective decisions about what society deems important and who may claim public resources. For instance, if education or healthcare policiesdiscriminate against the children of single, unmarried parents, we would find that deeply objectionable.

Yet, housing policies continue to disadvantage single parents, expressing the assumption that as a society, we are fine with these families being penalised. Whether this is consciously intended or not, relegating their housing problems to the realm of philanthropy amounts to further acceptance of this assumption.

In Singapore, where HDB housing dominates and private housing caters mainly to people with higher incomes, barring single parents from public housing discriminates against, not just single parents in general, but lower-income single parents in particular.

The issue at hand is therefore also one of fairness and equality: Public goods should be evenly accessible to all members of society. When we see unevenness in our public policy, we should work harder to resolve it collectively, rather than push the resolution to individual actors such as civil society.

This is not to say that civil society cannot contribute; for instance, it may conduct research and raise public awareness of housing problems. It can engage decision-makers and recommend changes to housing policies, as Aware - the Association of Women for Action and Research - has done in a recent research report and petition campaign.

But we must be clear that certain public goods cannot and should not be provided through individual initiatives. Public goods must remain public goods.

•Ng Kok Hoe is an assistant professor at the Lee Kuan Yew School of Public Policy, National University of Singapore and Teo You Yenn is an associate professor and head of sociology at Nanyang Technological University.