The International Maritime Organisation (IMO) agreed to force energy efficiency design standards on new ships from 2013, but developing countries will probably delay implementation until 2017 or 2019.
Forty-eight countries voted in favour of adopting a mandatory energy-efficiency design index (EEDI) for new ships at a meeting of the IMO's marine environment protection committee in London on Friday, while five were against and 12 abstained, sources said.
More extensive market-based measures such as a levy on the heavily-polluting bunker fuels used by most ships, or their inclusion in carbon trading, were not discussed at the meeting.
The deal does not contain any CO2 emissions reduction targets, and is eventually expected to slow rather than reduce the growth of maritime CO2 pollution.
According to an IMO study, shipping emissions could grow by 150 to 250% by 2050 without regulation.
The EEDI will force new ships to meet a minimum level of energy efficiency. Ships built between 2015 and 2019 will need to improve their efficiency by 10%, rising to 20% between 2020 and 2024 and 30% for ships delivered after 2024.
However, a group of countries led by China, Brazil, Saudi Arabia and South Africa secured a waiver for new ships registered in developing nations.
The rift between developed and developing countries resembles differences over emissions cuts in failed UN climate talks.
If countries choose to apply the waiver for a newly delivered ship, implementation of the index will be delayed from between four and six-and-a-half years from 2013, depending on the nature of the ship's contract.
"Adopting the EEDI is the right step but the long delay weakens its short to medium term impact significantly. If the IMO does not deliver action quickly now on existing ships, it will be up to the EU to take the lead at a regional level," said Bill Hemmings, director of Brussels-based non-governmental organisation Transport & Environment.
A waiver for some countries could mean that EU shipbuilders, for example, could build and flag a ship in a developing country without having to comply with the new regulation for some time.
EURACTIV with Reuters