Drivers could face a HK$5 increase in the toll for the Cross-Harbour Tunnel, with a corresponding HK$5 reduction for the Eastern Harbour Tunnel, in a plan designed to ease traffic congestion.
Chief Executive Leung Chun-ying said he would consult the public on a plan to adjust tunnel tolls during the first half of the year.
Although he did not say by how much the tolls would change, a consultant commissioned in 2010 to study congestion around the tunnels made proposals.
The study suggested raising the cost for private cars to use the Cross-Harbour Tunnel, from Hung Hom to Causeway Bay, from HK$20 to HK$25, and decreasing that for using the eastern crossing, from Quarry Bay to Cha Kwo Ling, from HK$25 to HK$20.
It said such an arrangement could divert 4,300 of the 120,000 vehicles passing through the government-owned Cross-Harbour Tunnel each day to the eastern crossing, which is used by 69,000 vehicles per day.
Leung said the government may compensate the owner of the eastern crossing, the New Hong Kong Tunnel Company, for any loss in revenue.
The third harbour tunnel - the privately run Western Harbour Crossing, which runs from West Kowloon to Sai Ying Pun - charges cars a toll of HK$55 per crossing.
A spokeswoman for the New Hong Kong Tunnel Company said it was open to the government's suggestion of a lower toll if it could ease traffic in the Cross-Harbour Tunnel.
The company's application to increase tolls by about 40 per cent was turned down in October.
Dr Hung Wing-tat, a transport expert at Polytechnic University, said if the government adjusted toll prices it should focus on commercial vehicles, such as vans. Vehicles transporting goods are charged between HK$15 and HK$30 to use the Cross-Harbour Tunnel and HK$38 to HK$75 to use the eastern tunnel.
"You only need to divert 20,000 vehicles from the Cross-Harbour Tunnel to the eastern tunnel to alleviate congestion," Hung said.
"There are 50,000 light-goods vans going through the Cross- Harbour Tunnel every day. If the toll discrepancies are narrowed, they'll change route."