The Carnival Corporation-owned brand had pleaded guilty in the US to seven charges of polluting the seas and then covering it up.

It is the largest fine to ever be levied for causing deliberate pollution from a ship and comes following an incident on board the Caribbean Princess in August 2013 when an engineer reported an illegal dump off the English coast.

The case was investigated by the British Maritime and Coastguard Agency (MCA) which found there had been two dumping incidents, one of which saw 4,227 gallons of the waste dumped by the Princess Cruise Lines ship in August 2013.

At the same time as making the dump, engineers simultaneously ran clean seawater through the ship’s overboard equipment in order to create a false digital record for a legitimate discharge.

Once senior ship engineers discovered that the whistleblower had informed the authorities of the practice, they dismantled the pipe and told crew members to lie.

However, the investigation revealed the ship had been making illegal dumps through a bypass ’magic pipe’ since 2005.

It was also found that two other illegal practices concerning discharges were found to have taken place on board Caribbean Princess, as well as four other Princess ships including Star Princess, Grand Princess, Coral Princess and Golden Princess.

US Attorney for the Southern District of Florida Wilfredo Ferrer said: “The conduct being addressed today is particularly troubling because the Carnival family of companies has a documented history of environmental violations, including in the Southern District of Florida. 

“Our hope is that all companies abide by regulations that are in place to protect our natural resources and prevent environmental harm. 

“Today’s case should send a powerful message to other companies that the US government will continue to enforce a zero tolerance policy for deliberate ocean dumping that endangers the countless animals, marine life and humans who rely on clean water to survive.”

Assistant attorney for the department of justice’s environment and natural resources division General John Cruden added: “The pollution in this case was the result of more than just bad actors on one ship.

“It reflects very poorly on Princess’s culture and management.  This is a company that knew better and should have done better. 

“Hopefully the outcome of this case has the potential not just to chart a new course for this company, but for other companies as well.”

A statement from Princess Cruises read: “We are extremely disappointed about the inexcusable actions of our employees who violated our policies and environmental law when they bypassed our bilge water treatment system and discharged untreated bilge water into the ocean.

“When we became aware of this back in August 2013, our headquarters management cooperated with the US Department of Justice (DOJ), the US Coast Guard and at the same time we launched our own internal investigation to learn all that we could about what happened.

“As a result of our investigation we discovered practices, on some other ships, where we were operating out of policy and in violation of environmental law.  We have reached a plea agreement with the DOJ, which was announced today.

“Although we had policies and procedures in place, it became apparent they were not fully effective. We are very sorry that this happened and have taken additional steps to ensure we meet or exceed all environmental requirements.

“In fact, over the past three years we have implemented a number of corrective measures to improve our oversight and accountability. For example, we completely restructured our entire fleet operations organization including new leadership.

“We also increased the scope and frequency of our training, and proactively invested millions of dollars to upgrade our equipment to new ship standards to ensure compliance with all environmental regulations.

“The marine environment is incredibly important to us and we are using this experience to further improve our operations.  Princess Cruises stands committed to environmental practices that protect our oceans.”