The Society for Community Organisation on Sunday called on the government to increase its quota for non-elderly singleton applicants for public housing and include them into its performance target, pointing out that poor living conditions affected their work as well as their mental health.

The NGO estimated that that there are nearly 40,000 single, non-elderly people living in subdivided units such as cubicles and caged homes.

"For example there are bed bugs, there're rats and then they cannot fall asleep... they [don't] have enough energy to work well, sometimes they will be unemployed," said SoCo's deputy director, Sze Lai-shan.

Sze said poor living conditions led to stress and a lack of rest, affecting their work performance and chances of upward mobility, with some reporting of having developed mental health illnesses.

Single, non-elderly public housing applicants are put under a quota and points system that look at factors such as their age and how long they have been waiting in queue, and Sze said they may have to wait for more than a decade to be assigned a public flat.

Currently, the average wait for a public housing unit for families and elderly one-person applicants is around six years.

Sze called on the government to add single, non-elderly people into its performance goals in public housing provision, adding that there should also be subsidies to help ease their financial burden.

She said the lack of support for some younger and single applicants is often overlooked.

"They [don't have] any support, and once they're unemployed they're immediately poor and nobody can help them," Sze said. "It seems they're abandoned by society, marginalised by society, and I think they feel hopeless."