The Paris MOU port state organisation has seen the number of ship bans rise in 2017.
It revealed in its annual report that it had to bar 33 vessels from its ports last year, up from 20 in 2016.
All but three of these were for multiple detentions after safety checks, but the others were banned for failing to call at an indicated repair yard.
A total of 10 ships have been barred for a second time.
Over a three-year period, Moldova, Tanzania and Togo have recorded the highest number of bans.
After a slight decrease in the total number of inspections last year, the number has increased in 2017 to 17,916.
The increase of the detention percentage from 3.42% in 2015 to 3.84% in 2016 has stabilised this year at 3.82%.
The level of detainable deficiencies has also stabilised this year to 3,706, from 3,781 in 2016.
The five most frequently recorded deficiencies in 2017 were ISM (4.4%, 1,774), fire doors/openings in fire-resisting divisions (2.5%, 1024), nautical publications (2.3%, 929), charts (2.0%, 797) and voyage or passage plan (1.5%, 594). The first four are consistent with 2016.
There were two new entries to the white list of flag states: Poland and South Korea.
Iran, Kazakhstan, Russia and the US moved from white to grey, while Tuvalu, which was not listed last year, also entered the grey list.
New to the black list is Ukraine.
The Republic of the Congo recorded the worst performance for the second year in a row.
