What do the terms "marine reserve" and "marine-protected area" conjure up for you? Places in which, perhaps, wildlife is protected? In which the damaging activities permitted in other parts of the sea – such as trawling and dredging – are banned? Wrong.

A marine-protected area in the United Kingdom is an area inside a line drawn on a map - and that's about it. In most cases, the fishing industry can continue to rip up the seabed, overharvest the fish and shellfish, and cause all the other kinds of damage it is permitted to inflict in the rest of this country's territorial waters. With three tiny exceptions, our marine reserves are nothing but paper parks.

The exceptions are the pockets of sea around Lundy Island in the Bristol Channel, Lamlash Bay on the Isle of Arran and Flamborough Head in Yorkshire. Together they occupy a grand total of 0.01% of British waters. These are the country's only "no take zones": places in which fishing and other extractive activities are banned.

After conducting a massive review of the evidence, in 2004 the Royal Commission on Environmental Pollution proposed that 30% of the United Kingdom's waters should be designated no-take zones. In 2009 a coalition of environmental groups launched a petition with the same aim: it gathered 500,000 signatures. But this didn't make a damn bit of difference to either the Labour or the coalition government.

The government is now in breach of its promise to designate an "ecologically coherent" network of marine conservation zones by 2012. The excuse it gives for the delay is that "there are a number of gaps and limitations in the scientific evidence base". But as the Royal Commission pointed out in 2004, the seas around this country "have been scrutinised in great detail since at least the mid-19th century", and the data is easily sufficient "to design comprehensive, representative and adequate networks of marine protected areas for UK waters." Perhaps unsurprisingly, the commission, which often voiced inconvenient truths, was shut down by David Cameron's government soon after it took office.

The Westminster government originally agreed to protect 127 sites in English waters, but now it appears to be paring the list down. Within these sites, only the "vulnerable features" will actually be protected; elsewhere it will be business as usual. If the government's record so far is anything to go by, the vulnerable features will amount to a few handkerchiefs of seabed. The remainder of these "conservation zones" can continue to be pulverised by beam trawlers and scallop dredgers.

But even if all 127 proposed marine conservation zones were to be designated, and even if the entire area of these zones were to be protected, that would account for a total of 0.5% of our seas: one sixtieth of the area recommended by the Royal Commission. In Wales the situation is even worse. The government there says it will consider "no more than three to four sites" , covering 0.15% of its seas.

So what about all those other marine reserves, such as our special areas of conservation? These are supposed to offer the highest level of protection available under European law, and are officially described as "strictly protected sites". Surely they offer our wildlife some protection? Wrong again.

The Marine Conservation Society has produced a gut-wrenching catalogue of the damage being done to these places by scallop dredgers, rock-hoppers (boats towing gear which turns over boulders to get at the fish sheltering among them) and all kinds of other destructive devices. If they are banned at all, it is only from a few small corners of the "strictly protected sites", often by voluntary agreement, and almost always reactively, after extensive damage has already been done.

The idea of actually protecting special areas of conservation, in their totality, in advance and by law, seems to be unthinkable to our governments. As Client Earth and the Marine Conservation Society point out, this puts the UK in breach of the European habitats directive.

The issue has come to a head once more with reports that scallop dredgers have been operating, apparently for the first time, in two recommended Marine Conservation Zones (Holderness Offshore and Inner Silver Pit) and one candidate special area of conservation (Inner Dowsing) in the North Sea.

The UK has a fleet of nomadic scallop dredgers, mostly based in Scotland and the Isle of Man, which travel from one conservation area to another, ripping them to shreds, aware that our governments will do nothing to stop them. Scallop dredgers operate by raking through the seabed with long metal teeth, dislodging the shellfish and trapping them in a net whose underside is made of chain mail. The teeth rip through the other lifeforms in their path; the steel mesh smashes the animals missed by the teeth. It is hard to think of a more effective method of destroying marine life, yet it is permitted in most of our special areas of conservation and other marine reserves.

The Marine Management Organisation, which is supposed to protect these places, merely wrings its hands. It knows it must apply the government's universal policy: that nothing should interfere with business, however damaging it is, however much it might harm the natural environment and even other businesses. (Local fishermen say that the scallop dredgers in just one of these sites have recently caused £100,000 of damage to their gear. They are likely to have done even greater damage to the fisheries on which local boats rely).

The chances of Richard Benyon, our fisheries minister, whose crashing conflicts of interest I exposed last month, demanding the protection of anything but the profits of the most destructive and short-sighted industries appear to be close to zero. It's intensely frustrating for anyone who loves the marine environment, and it's another powerful indication that "the greenest government ever" is even more destructive than its predecessors.

monbiot.com