The shortage of access to public toilets in Guangzhou subway stations sparked public outcry after a boy was pictured defecating in a subway car.

The photo of the child squatting in a subway carriage went viral after it was posted on the micro-blogging website Sina Weibo on Nov 10.

It immediately fueled complaints about insufficient access to public toilets - only 16 of Guangzhou's more than 100 metro stations have public toilets.

An official from Guangzhou Metro who did not want to be identified said the company has been urged to have the plans for new stations include toilets to help ease the shortage.

"Many deputies of the city people's congress, members of local committees of the Chinese People's Political Consultative Conference and residents have suggested we install mobile toilets near metro stations to deal with the problem, and we are discussing such a plan," he added.

Meanwhile, the corporation is trying to guide passengers to use the public restrooms near metro stations, he said.

Han Zhipeng, a member of the CPPCC Guangzhou committee, wrote on his micro blog that the subway station should give commuters access to staff toilets upon request.

The operating company could learn from Shanghai Metro, he said, which initially installed temporary toilets for commuters.

Lan Tian, a media officer at Shanghai Metro's operation management center, said the company has gone a long way toward providing restrooms for commuters.

"We didn't realize commuters would need toilets when Shanghai built Lines 1 and 2," he said.

When the company began to receive complaints, it could only provide temporary toilets, "but waste disposal was a problem", he said.

The company later installed "green" toilets that disposed of waste using biotechnology. However, because of the large volume of passengers, the toilets broke down at times, and the company had to close the toilets.

The problem was solved in 2009 when Shanghai Metro introduced a system that uses vacuum pumps to transfer waste to the city's sewage network.

The shortage of public toilets in subway stations has long been a subject of complaint. In some cities where China's earliest subway lines were built, before 2000, subways provided no public restrooms.

In Beijing, which has the world's fourth-largest subway network, only nine stations in the east section of Line 1, the oldest line, lack toilets.

After that section went into operation in 2000, the stations without toilets became a source of complaints.

Beijing Subway, the State-owned company in charge of most subway lines' operation in the capital, installed temporary toilets in those nine stations in response.

In 2005, the company was sued for charging commuters to use the temporary toilets and then not providing invoices.

Beijing No 1 Intermediate People's Court ruled that the company took over the right to operate the subway lines after the stations were built and in consequence was not responsible for providing restrooms, and that it could hardly be faulted for nevertheless paying to install temporary toilets.

Tianjin has the mainland's second-oldest line, built in 1984. All eight of its stations also lack toilets.

New subway networks in Xi'an, Shenyang and Shenzhen all have toilets in stations.

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Shi Yingying in Shanghai, Li Xiang in Tianjin, Ma Lie in Xi'an and Liu Ce in Shenyang contributed to this story.