Some cruiseships are responsible for pollution levels that are higher than in the world’s most polluted cities, an investigation by Channel 4's Dispatches has found.

In an undercover investigation broadcast on UK TV yesterday, a vessel owned by Carnival Corp’s British brand P&O Cruises was found to emit high levels of “ultra-fine particles”.

Dispatches used a P-Trak ultra-fine particle counter on the 77,499-gt Oceana (built 2000).