The government is being urged to impose emission controls and incentives to reduce pollution at the Kai Tak cruise terminal.
Friends of the Earth has called on Chief Executive Leung Chun-ying to encourage cruise operators to make ships shorepower capable or to use cleaner fuel.
Leung said on Wednesday in his policy address that the government planned to seek funding from the legislature to install onshore power facilities for cruise vessels to use while berthing to minimise their emissions.
But Friends of the Earth said immediate action should be taken to control emissions, as seeking the legislature's approval, followed by the installation process, would take too long.
"The government should not only care about the profit made by [cruises], but [also] the emission problem posing an immediate threat to the health of residents," said Melonie Chau Yuet-cheung, senior environmental affairs officer of the group.
Chau likened cruise vessels to "mini-power plants" emitting huge amounts of suspended particles and greenhouse gases, which far exceeded the government's air quality objectives.
She said that according to think tank Civic Exchange, vessels visiting the Ocean Terminal emitted 252 tonnes of sulphur dioxide in 2007 - comparable to the 286 tonnes of vehicle emissions in Hong Kong in 2010.
The green group estimates that 380,000 residents in the East Kowloon area will be affected by the vessel emissions.
"Incentives, such as a reduction of berthing fees, should be given to companies for using low sulphur diesel or onshore electric power," said Chau, adding that, in the longer term, the government should force all vessels berthing at the terminal to use onshore electricity.
As of mid-2011, out of the world's 270 cruise vessels, only 18 could use onshore power, reported a cruise industry journal. Among the cruise firms scheduled to berth their vessels at Kai Tak, only Princess Cruises and Holland America own vessels with onshore power facilities.
With the opening of the first berth at the terminal at the former Kai Tak runway in June, the city can accommodate the world's largest cruise vessels, which were too big for Ocean Terminal.