A minibus association on Friday warned that some fares will go up in light of the government's changes to cross-harbour tunnel tolls.

Under congestion charge plans to be rolled out from August 2, minibuses, buses and other commercial vehicles using any of the three tunnels will be charged HK$50 per trip, at any time of day.

While this will mean a reduction for such vehicles in some cases, minibuses using the Cross-Harbour Tunnel will be charged five times the current rate.

"We will have to pass on the cost to passengers. We are facing difficulties in operation and it doesn't make sense to have an extra HK$40 toll," Ling Chi-keung, who chairs the Public Light Bus General Association, said on an RTHK programme.

"There will be a HK$1 or HK$2 fare hike," he added.

The chairman of the Hong Kong Courier Association, Ng Kwong, told the same programme that his industry shares concerns about the Cross-Harbour Tunnel fees.

Ng said most couriers currently opt for this tunnel because it's the cheapest, and the planned toll increase will hit them hard.

"Tolls for taxis will be set at HK$25 for the three tunnels. But why will the tolls for commercial vehicles be HK$50, double that of taxis? Why is the price increase for the Cross-Harbour Tunnel so big?" he questioned.

"Lowering the tolls for the other tunnels can definitely redistribute traffic, but raising the toll for the Cross-Harbour Tunnel is increasing our costs."

Ng said the industry will have no choice but to raise the price of courier services by up to 20 percent.

He added that a flat-rate toll fee of HK$30 or HK$35 for commercial vehicles would be more appropriate.