Global shipping companies have spent millions rigging vessels with “cheat devices” that circumvent new environmental legislation by dumping pollution into the sea instead of the air, The Independent can reveal.

More than £9.7m has been spent on the devices, known as open-loop scrubbers, which extract sulphur from the exhaust fumes of ships that run on heavy fuel oil.

This means the vessels meet standards demanded by the International Maritime Organisation (IMO) that kick in on 1 January.

However, the sulphur emitted by the ships is simply re-routed from the exhaust and expelled into the water around the ships, which not only greatly increases the volume of pollutants being pumped into the sea, but also increases carbon dioxide emissions.

The change could have a devastating effect on wildlife in British waters and around the world, experts have warned.