Plans for massive American-style motorways and new roads that slice through sensitive nature areas and historic sites are among a string of new transport schemes to be considered by the Government.

The Observer has uncovered details of more than 30 highly controversial plans to be submitted to Transport Secretary Stephen Byers.

Most have the backing of the Highways Agency, government consultants and local authorities. Among the most controversial ones are:

· Plans to widen the London orbital motorway M25 to 12 lanes around congested junctions and 10 lanes in other parts.

· A proposal to create a huge 10-lane orbital motorway around the southern and western sides of Birmingham. It would be fed by several new bypasses through unspoilt countryside near Wolverhampton and Stourbridge.

· Widening the M6 between Birmingham and Manchester to 10 lanes.

· A series of new bypasses and link roads in the South West around the scenic Cheddar Valley to widen lorry routes between the M4 and M5. The proposed new roads would pass close to historic Brattan Castle and the chalk 'white horse' near Westbury.

· Expanding the A66 to dual carriageway right across the north Pennines from Scotch Corner to Penrith.

· New bypass for Mottram and Tintwhistle cutting into the Peak District and local Swallows Wood nature reserve and two schemes in Norfolk affecting unspoilt heathland and the broads.

Environmental and transport groups attacked news of the plans last week and said the schemes would turn some areas into 'Los Angeles-style traffic jungles' over the next decade. A spokesman for Transport 2000 said the Government would face court challenges if it pushed ahead with road schemes through dedicated Sites of Special Scientific Interest.

Director Lynn Sloman said: 'If Ministers say yes to all these new schemes, there will be a plague of cars and lorries on our already overcrowded roads through countless communities.'

Environmentalists claim that the Government has failed to keep its promises to cut traffic and improve public transport. Despite announcing a 10-year £180bn transport plan, Labour has so far presided over a crumbling railway system and bus services that are too infrequent and expensive. Ministers have allowed a creeping return to a pro-roadbuilding agenda in the face of accusations from the motoring lobby of being anti-car.

National motoring organisations such as the AA and the RAC Foundation said the planned schemes were no more than carefully targeted improvements to ease traffic bottlenecks and speed up journeys. The AA said road-building in Britain was at a 30-year low and that the network was not sufficient to support the strong economy.

John Dawson, policy director at the AA, said: 'Even if all the road plans now about to go before Ministers get the go-ahead, it will hardly dent congestion over the next 10 years.'

Campaigners are also concerned that the European Commission has softened its support of environmentally friendly measures, making it more difficult for Britain to press ahead with measures designed to reduce traffic.

Transport Commissioner Loyola de Palacio told The Observer: 'Road traffic is going to increase and there are bottlenecks. We must build new infrastructure, we cannot avoid it. Trains, yes, but also new roads and airports, even if it is controversial. Mobility is crucial for our competitiveness.'