WWF is issuing its lament for the cod as it launches Orca, its oceans recovery campaign, designed to raise awareness and prompt action on marine problems.
The UK's distinctive contribution to world cuisine, fish and chips, could disappear unless changes are made, conservationists say.
WWF, the global environment network, says cod, the traditional partner of the fried potatoes, faces severe depletion unless marine resources are managed better.
WWF wants some areas of the sea to be placed out of bounds to fishing vessels, to give the shoals a chance to recover.
It has secured the agreement of the prime minister's official residence, 10 Downing Street, to accept what it describes as Number 10's first-ever internet petition, seeking government commitment to increased marine protection and to sustainable fisheries management.
Recovery
People who sign the petition online will have their names and addresses recorded on a database which will be available to Downing Street staff.
WWF is issuing its lament for the cod as it launches Orca, its oceans recovery campaign, designed to raise awareness and prompt action on marine problems.
It says these include over-fishing, pollution from land and sea, mineral extraction, climate change, and the arrival in UK waters of alien species.
Cod, WWF says, are affected in several ways: poor management of the stocks allows them to be fished unsustainably, warmer water temperatures adversely affect their reproduction rates, and pollution interferes with the eggs and larvae.
It says the fish are in desperate straits:
It also wants a stronger network of marine protected areas, to give protection to cold water coral reefs, seagrass meadows, kelp forests and other submarine habitats.
Although UK marine species include corals, sea horses, turtles, sharks and cetaceans, only one per cent of the country's seas are protected, far less than on land.
Matthew Davis of WWF said: "Unless we take action to regenerate fish stocks, traditional fish and chips may soon become a dish of the past.
"This isn't just a threat to ocean wildlife, it's a threat to our cultural heritage. The commercial extinction of fish stocks could jeopardise the jobs of the 15,000 full-time and 3,500 part-time fishermen in the UK.
Investment
"In the face of ineffective management of fish stocks, fishermen and environmentalists share the same goal - abundant fish stocks in healthy seas.
"Fishing-free zones and a stronger network of marine protected areas are simply an investment in the future."
WWF and the Scottish Fishermen's Federation launched a joint initiative last March, calling for specific changes to local and European fisheries management.