The 12 per cent slide in Hong Kong's container throughput last month underpinned a structural problem exacerbated by a strike at one of the terminals last month, a port operator said.
Hung Tam-yuen, the chairman of Turbo Maritime, which has operated barge services to mainland cities for more than 20 years, is worried that an increasing number of exporters will switch to ports in Shenzhen and Nansha, Guangzhou.
Buyers in the United States and Europe were told to use mainland ports to avoid any disruptions caused by the strike last month, Hung said.
The 40-day strike at the world's fourth-busiest port caused a backlog of containers at the dock that needed seven days to clear.
More than 60 per cent of the containers handled in Hong Kong carried goods made in Guangdong province.
Manufacturer and buyers use Hong Kong ports mainly for the perceived higher efficiency in the city.
But these advantages are disappearing as mainland ports have modernised over the past 10 years.
"When they find that the difference in efficiency is not that much between Hong Kong and Shenzhen, they will switch to the mainland for good," Hung said.
Last month, Hung's company moved 8,000 20-foot equivalent units (teu), down 20 per cent from a year ago.
Hong Kong's container throughput dropped 12.2 per cent last month to 1.73 million teu.
Throughput at the Kwai Tsing container terminals decreased 10.7 per cent while the river trade terminals recorded a 17 per cent decline.
Shenzhen Port, on the other hand, handled 1.8 million teu, an increase of 2.2 per cent.
Guangzhou Port recorded a 0.2 per cent rise to 1.3 million teu.
"It is more of a structural problem than a one-off problem for Hong Kong losing out to shipments to Shenzhen," said Peter Wong, the managing director of DP World Asia Pacific, which operates Terminal 3 in Hong Kong.
"The infrastructure of our terminals is lagging our rivals across the border," Wong said.
"It's crucial for the government to do something to facilitate the operation of our barge service to lure more transshipment cargo back to Hong Kong."