The UK register took a hit from Brexit on Tuesday as P&O Ferries said it was reflagging the rest of its cross-Channel fleet to Cyprus.
A company spokesman told Cypriot state-run news agency CNA the ships involved are the 30,600-gt Pride of Canterbury (built 1991) and Pride of Kent (built 1992), the 28,100-gt Pride of Burgundy (built 1993) and the 23,000-gt European Seaway (built 1991).
It initially flagged two Dover to Calais vessels to Cyprus last year.
"In advance of Britain leaving the European Union on March 29, 2019, we undertook a review of the flag status of our ships on the English Channel," the spokesman said.
"For operational and accounting reasons, we have concluded that the best course of action is to re-flag all ships to be under the Cyprus flag."
The move will cut tax bills by keeping the vessels within the EU, the report said.
