Australia says it will ban fishermen from about one third of the Great Barrier Reef to protect the world's largest living structure from the impact of human activity.
Australia's greatest natural icon
The coral reef is under threat from record-high temperatures, over-fishing and pollution.
Environment Minister David Kemp said the plan would increase so-called green zones, where commercial and recreational fishing is banned, from 5% of the 2,000-kilometre (1,200-mile) reef to over 30%, prompting instant protests from fishermen.
"The Great Barrier Reef is suffering very considerable pressures at the moment from increasing usage by tourists, by fishers, by the local communities," Mr Kemp said.
"It is very important that we give the reef proper protection for the future. The reef is Australia's greatest natural icon."
The Great Barrier Reef, situated off Queensland state in Australia's northeast, injects an estimated A$1.5bn ($975m) into the economy each year through tourism and fishing.
Mr Kemp said the plan, expected to be approved later this year, would boost the area subject to high protection to 114,000 square km (44,020 sq miles) from 16,000 square km (6,178 sq miles), creating the world's largest network of protected marine areas.
This would help boost declining fish stocks by protecting breeding grounds.
Companies and individuals caught breaching green zone rules would face very heavy fines.
The expanded protection area only just meets environmentalists' demands that 30-50% of the reef be declared a sanctuary to sustain its long-term health.
The Green Party said the plan needed to be backed up with action on land clearing and global warming, as chemical run-off from cattle grazing, sugarcane growing and urban development was polluting the reef.
But the commercial fishing industry warned the plan could devastate fishing firms and small communities.
"More fishermen will be competing over fewer fish," Duncan Souter, head of the Queensland Seafood Industry Association, said.