But 15 acres of the coral reef, which is home to critically endangered turtles, could be destroyed to make way for two cruise ship docks as part of plans to boost tourism.

Environmental campaigners warn the George Town Harbour project will see 22 acres of the seabed dredged, and silt sedimentation will turn the “crystal-clear aquamarine waters to murky white”.

In December, the first publicly initiated referendum on the islands will decide the reef's future, after 25 per cent of the electorate signed a petition to take the decision to a vote.

There are fears it may not save the reef as campaigners claim the Government has withheld the latest designs for the docks, and the date of the vote coming so close to Christmas will mean many residents are on holiday.

“The marine environment is the heritage of the Caymanian people and decisions made today will have consequences for generations to come,” said Shirely Roulstone, of the Cruise Port Referendum (CPR) Cayman campaign group.

“We must be responsible custodians of our precious natural resources.”

The seabed will be dredged and two deep water piers constructed on pilings to allow marine life move underneath as part of the project.

The first Environmental Impact Assessment (EIA), submitted in 2015, said 15 acres of coral reef habitat would be permanently removed.

But the designs have been altered, following the selection of the preferred bidder, Verdant Isle Port Partners (VIPP) in July, and have not been subjected to a new EIA.

Campaigners have called for the full plans to be released and a new EIA carried out before the referendum.

This week the Cayman Islands Government (CIG) and VIPP have confirmed that the new plans will lead to an overall reduction in the dredge footprint, impact on coral and adverse environmental impact.

VIPP told The Daily Telegraph they will be conducting a “relocation” programme to try and save some of the critically endangered corals in the area, such as the Elkhorn and Staghorn.

Citing multiple studies and past successes with repairing damaged reefs, they hope to translocate much of the affected coral prior to dredging.

They also have optimistic plans for ‘coral gardening’, where fragments of healthy coral will be grown in tanks, before replanting in nearby reefs - with a goal of replanting one million corals.

But they admitted: “It is clear that coral relocation will never completely mitigate impacts of proposed projects.”

The individual cruise liners involved in the project - Royal Caribbean Cruises and Carnival Cruise Line - have also come under fire, after they separately pledged to work with conservation NGOs, WWF and The Nature Conservatory, to “ensure the long-term health of the oceans” in recent years.

Charlie Butt, Caribbean Territories Manager for the RSPB, said it is “difficult to believe” the companies would back the project if they understood the true environmental impact.

The RSPB are concerned the plans would lead to a “net loss of globally threatened wildlife", such as the critically endangered Hawksbill Turtle, he said.

“Whilst we welcome the sustainability commitments of the two cruise liner companies involved, it is difficult to believe that they would consider backing this plan if they knew that at least 15 acres of world-class coral reefs - one of the Cayman Islands’ main tourist attractions - would be permanently lost as a result,” he said.

The Cayman Islands is one of the UK’s Overseas Territories (UKOTs), and estimates state 94 per cent of the UK’s biodiversity is located in our OTs.

The UK government has made international commitments to safeguard this biodiversity, under the Convention on Biological Diversity.

Yet repeated calls by CPR Cayman and RSPB for consultations with Tariq Ahmad, the Minister for Commonwealth who is responsible for the UKOTs, have been refused or gone unanswered.

An FCO spokesman said: “Environmental protection is an area of devolved responsibility to the locally elected Government.

"Lord Ahmad discussed the environmental impact of the proposed project with the Government and the Opposition when he visited the Cayman Islands in June.

"Our Governor talks regularly about this issue with all those involved, including the Premier and CPR.”

Last week the Islands Premier, Alden McLaughlin, told local news outlet Cayman Compass there was enough information in the public domain for people to make an informed decision, saying the cost, location and concept designs had all been revealed.

The CIG has now said the updated design will be released in the coming days.