Twenty-seven new marine conservation zones (MCZs) will be created in English seas on Thursday to protect seahorses, coral reefs, oyster beds and other marine life.
But the number is four less than ministers proposed and just one-fifth of the 127 zones recommended by the government's own consultation.
The seas around England are some of richest marine environments in the world, with dense forests of seaweed, many fish and crustacean species and schools of dolphins, but dredging and bottom-trawling for fish, prawns and aggregates have devastated large areas.
"We very much see the new MCZs as the beginning and not an end," said environment minister George Eustice, who said consultation on two more tranches of MCZs would start in 2015. He added: "It is important to remember that MCZs are only one part of the jigsaw. Over 500 marine protected areas already exist around the UK."
The 27 zones cover 9,700 kilometres squared (km2) from the Aln estuary in the north-east to Beachy Head and Chesil Beach in the south and Padstow Bay and the Scilly Isles in the south-west. Together with the 30,000km2 already protected, 9% of all UK waters and one-quarter of inshore waters now have some form of protection – though critics have called the existing protected areas "paper parks" that do not stop the most damaging practices.
Professor Callum Roberts, a marine expert at the University of York who led 86 marine scientists in condemning the government in April for reneging on the 127 MCZs recommended by an earlier £8m consultation, said: "The 27 is far, far away from where we need to be."
Ministers have argued that the economic cost to fishing and ports of some proposed zones would be too great, but Roberts was blunt: "It's bollocks. These MCZs will not put fishermen out of jobs: they will protect them in the long run."
Roberts said the possibility of more MCZs in future provided an opportunity: "If science is put at the helm it will be worth waiting for."
Joan Edwards, the Wildlife Trusts' head of living seas, welcomed the news: "Marine protection is an issue which matters to anyone who has ever spent happy afternoons exploring rock pools or been enchanted by chance encounters with dolphins, whales or one of the many other captivating species we enjoy in our waters."
But she said the completion of an "ecologically coherent network of marine-protected areas was desperately needed", particularly to ensure species with large ranges like basking sharks and sea birds were protected.
Dr Jean-Luc Solandt, biodiversity policy officer at the Marine Conservation Society, said the current way of creating MCZs was too complex and costly, as each part of each zone had to be assessed. "Protecting whole zones is much more simple and visionary as it allows larger areas of seabed to actually recover. That is what our sites need – actual recovery."
Barry Gardiner, Labour's environment minister, said: "Once again we see this government's failure to implement proper science. The scientific purpose was to create an ecologically coherent and resilient network of 127 sites and 65 reference areas that would safeguard and enhance the biodiversity of our marine heritage. The government is not only 100 sites light but predictably it has failed to specify how the inshore fisheries conservation authorities are going to be resourced to monitor, manage and enforce this new statutory obligation."
On Monday, 41 UK conservation groups issued a report stating that just four of the 25 nature and wildlife commitments made by the government were progressing well. It said the ministers were failing on the pledge to better protect the marine environment.
