The ICS had previously criticized the results as both fanciful and misleading.
Environmental organisations Seas At Risk and Transport & Environment (T&E) Wednesday in an emailed statement defended the validity of a recent report regarding the energy efficiency of newer-built ships compared with older vessels.
The report, which concluded that ships built in recent years were on average 10 percent less efficient than ships built before 1990, was dismissed and criticised by the International Chamber of Shipping (ICS) as "fanciful."
The ICS also attacked the report's methodology, in addition to claiming that T&E had twisted the reports findings for their own gain.
However, CE Delft, the group who was commissioned to create the report, defended its results and also stressed the caveat that their findings applied to design efficiency, not operational efficiency.
John Maggs, President, CSC
The ICS now needs to take the results seriously and show us why the EEDI targets shouldn't be reviewed
"One of the main reasons why modern ships have a design efficiency that is worse than ships built around 1990 is that modern ships are, on average, fuller (more block-like)," the company said.
"The reason for this is that when freight rates are high, it makes sense to build full ships because within draft and length constraints, they can transport more cargo than a more slender ship."
John Maggs, president of the Clean Shipping Coalition (CSC), also reiterated his support for the study and called for renewed attention towards the International Maritime Organization's current Energy Efficiency Design Index (EEDI) standards.
"As CE Delft has reiterated, its findings are based on the data and EIV/EEDI formulae which the IMO itself used," he said.
"The ICS now needs to take the results seriously and show us why the EEDI targets shouldn't be reviewed."
Seas At Risk and T&E are both members of the CSC.
The original report, which was released earlier this month, also claimed that containerships built 30 years ago have already exceeded EEDI standards set for new ships to be built in 2020.