MPs have criticised the "slow pace" of moves to protect the UK's seas, suggesting the Government lacks commitment to marine conservation.
The Government has designated just 27 "marine conservation zones" around England, although 127 sites were recommended by regional groups tasked with drawing up potential sites to protect ocean species and habitats.
A further 37 could be designated at the end of 2015 - progress which the parliamentary Environmental Audit Committee labelled as "unambitious" and called on ministers to move much more quickly to establish more protected areas of the seas.
"This slow pace has been disappointing and suggests a lack of Government commitment to this initiative", the committee said in a report on marine protected areas, which aim to prevent overfishing and ensure wildlife-rich, healthy seas.
The report also warned the Government had "unhelpfully moved the goalposts" by increasing the standard of evidence it needed to designate new protected areas.
Officials should adopt a precautionary principle, using the "best available" data to ensure that rare species or wildlife-rich stretches of seabed are not lost forever before they can be designated.
The Government should bring forward the programme, to designate more conservation zones in the next round in 2015, the report said.
Budget cuts at the Environment Department (Defra) mean the Government cannot demonstrate that the body in charge of managing the zones and enforcing protection measures, such as bans on types of fishing, has the resources to do so, the MPs said.
They urged ministers to set out a strategy for managing the 27 marine conservation zones and management plans for each individual site to show that they can be enforced.
The committee's chairwoman, Joan Walley, said: "Marine conservation zones can protect our seas from over-fishing and give species and habitats space to recover, ultimately benefiting people whose livelihoods depend on healthy seas.
"But the Government has been too slow in creating these zones, and it has failed to get coastal communities and fishermen on board.
"It is now well over four years since the launch of the programme, yet only 27 of the 127 sites recommended by independent project groups have been designated.
"The Government must stop trying to water down its pledge to protect our seas and move much more quickly to establish further protection zones and ensure they can be enforced."
She added: "When a rare species or biodiverse stretch of seabed is destroyed, it may be lost forever.
"The Government must therefore act on the best available evidence and base its decisions on new marine conservation zones on the precautionary principle, rather than demanding unobtainable evidence."
She also said it was "not acceptable" that the Marine Management Organisation (MMO) will not have management plans in place for existing conservation zones until 2016, and warned the Government must show the organisation's falling budget would not jeopardise the scheme.
Defra is responsible for creating marine conservation zones in English inshore waters and in offshore waters around England, Wales and Northern Ireland, as part of a Government commitment to a UK-wide "well-managed and ecologically coherent" network of marine protected areas.
Sarah North, Greenpeace UK head of oceans said: "This report is a damning indictment of government inaction on ocean protection.
"In failing to create marine protection zones in English waters, ministers have yet again left fish stocks and wildlife to the mercy of those who treat the oceans like a mine to be exploited, rather than a resource to be cherished.
"Instead of pandering to whichever vested interest group shouts the loudest, the Government should propose marine reserves that actively create benefits for our inshore and low-impact fishing fleet and protect our most sensitive habitats and species.
"They would then find allies in both green groups and in coastal communities. Together this would reinvigorate ocean ecosystems and bring life back to the towns and villages along our shores."
A Defra spokeswoman said: "We are doing more than ever to protect our marine environment, with 27 MCZs designated last year and a further two more phases of designation expected over the next few years.
"Management measures are currently being drawn up to ensure effective, tailored protection for each of the sites."