Government plans to strip a species-rich area of seabed off Sussex for sand and gravel to satisfy demand for new homes has been slammed by conservationists and fishermen.

Ministers are expected to authorise the dredging of millions of tonnes of aggregates from a 90-square-mile area south of Beachy Head.

Conservationists and fishermen's groups are outraged at the plan, which they claim could destroy a vast area of marine habitat and harm vital spawning grounds.

Six companies are lobbying for permission to extract up to 17 million tonnes of sand and gravel a year at a new dredging area 20 miles off the coast.

Ministers are believed to have approved the proposal in principle, although tonnages may initially be set lower than the industry wants.

Lisa Browning, regional marine officer for the Wildlife Trusts, said the Government risked breaking EU laws intended to protect fragile marine habitats.

She said the sand and pebbles strewn across the seabed were covered with corals, sponges, sea anemones, scallops, crabs, plaice and sole.

The area was the eastern Channel's most important spawning ground for herring.

Ms Browning said: "The worst-case scenario would be that ten or 20 years down the line we realise we have destroyed a really important marine habitat.

"There is the potential the habitat may never recover.

"We simply do not know enough about it. We don't know if it is a unique area or not.

"It may turn out there is a particular species or environment that is unique and that risk is the thing we are worried about."

Clive Pepe, of the Brighton-based environmental organisation riverOcean, said: "It does seem a bit of a reckless gamble with our marine habitats.

"If we are interested in protecting resources for future generations we should not be engaged in playing Russian roulette on this kind of scale."

Sand and gravel, increasingly difficult to obtain on land, is needed to help build the 200,000 new homes the Government plans for the South-East in the next 20 years.

Half the aggregates used by the construction industry in London and the South-East come from the seabed, a figure expected to increase because of the house-building boom.

Existing dredging grounds are becoming exhausted and regional planners want to grant new under-sea licences off East Sussex, where reserves are thought to total 250 million tonnes.

Sussex sea fisheries officer Tim Dapling said there were worries about the impact on fish stocks.

He said: "There is a lot of concern about it.

"We appreciate the fishery aspect has been looked at but I think there is some concern whether there is enough information to make a decision on the long-term impacts.

"The scale of extraction is such that it is not only for domestic use but it is for export as well. Is that a sustainable approach for the use of aggregates?"

Dr Andrew Bellamy, of the East Channel Association, formed by the companies bidding for 15-year dredging licences, said only a small amount of the seabed would be worked each year.

He said aggregates were needed at home and for export.

Sea life would return when dredging was complete and the seabed had already been damaged by commercial fishing.

Dr Bellamy said: "The areas we have put forward for dredging have been carefully selected to minimise the impact on things like marine life, the fishery and the coastline as well.

"We are not talking about any areas close to the Sussex coast. They are about half-way between England and France.

"We have done surveys of what marine life is present on the seabed and found the marine life is not unusual."

The Deputy Prime Minister's Office said licences would only be granted if it was satisfied there would be no adverse environmental impact on the seabed, sea life or the coast.

The Government is likely to earn tens of millions of pounds in royalties from the dredging operations.