Seafarers will be free to boycott voyages to South Korea amid growing concern over the jailing of senior officers from the oil tanker involved in the country’s worst oil spill, leading shipping organisations have said.

Jasprit Chawla, master of the Hebei Spirit, was jailed on December 10 for 18 months and Syam Chetan, the chief officer, for eight months. Their vessel, which had been sitting at anchor, spilt 10,800 tonnes of crude oil into the Yellow Sea off Daesan on December 7 2007 after being hit by an out-of-control barge.