The windswept, grey river mudflats of London's extreme east back on to the capital's bleakest wasteland. But a plan to transform the desolate landscape by building a six-lane road bridge over the Thames has sparked a revolt among London mayor Ken Livingstone's advisers.

Known as the Thames Gateway, a stretch of river from the Millennium Dome to the Essex border bisects a deprived area, where the gasworks of Beckton and Woolwich's crumbling piers face the down-at-heel estates of Thamesmead. Keen to attract businesses and jobs, the Greater London Authority has earmarked the area as the site for the capital's first new road bridge over the Thames since London Bridge was replaced in 1973.

Mr Livingstone wants to use receipts from the Dartford toll bridge in Kent to fund the £345m crossing - designed as a space-age steel structure with four lanes for cars and two for buses. Local residents and businesses are overwhelmingly in favour. But the idea has appalled environmentalists and been criticised by transport experts, who say it could make an uninviting area even less appealing.

Even Mr Livingstone's closest colleagues have attacked the plan. At a meeting last month of the mayor's Transport for London authority, board members were split five-five on the issue. For the first time since his election, Mr Livingstone used his casting vote as chairman to force the project through.

Among dissenters were two close colleagues from Mr Livingstone's GLC days - Paul Moore, and deputy chairman Dave Wetzel. Another "no" voter was David Begg, chairman of the government's commission for integrated transport, who said: "Unemployment in east London is high - but that's about people not having the right skills, not because they can't get around."

Key to the case for the Thames Gateway Bridge is a complaint that there is an "east-west divide" in river crossings. While west London has 26 road and river crossings, the east has just two - the Jubilee line and the Woolwich ferry - in a 26-mile stretch between the Blackwall and Dartford tunnels. The business lobby group London First says the river has become an intractable barrier. Thamesmead residents can see planes taking off from London City airport just a few hundred metres away. But if they want to fly, it is almost as quick for them to get to Gatwick in West Sussex.

Sainsbury's has a depot in Charlton, south-east London. But the roundabout route to get across the river means that stores on the north side are better served by a warehouse in Hertfordshire.

London First's transport spokeswoman, Michelle Washington, said: "These areas are vital to delivering the housing the government says will be needed in the south-east. We accept that roads on their own don't regenerate communities but it's not just about building a road - it's about creating links between people." She cited US bank Citigroup, which abandoned a plan to site an emergency backup centre in Lewisham, a few miles south of the river, because it feared staff from north London would struggle to get to work.

The bridge, which could be open in 2010, is ultimately intended to be part of a three-part package, alongside a new railway tunnel under the river in Woolwich and another road crossing in north Greenwich, near the Millennium Dome.

To use toll receipts from the Dartford Bridge, Mr Livingstone needs clearance from the transport secretary, Alistair Darling. The government is thought to be looking kindly upon the idea, having pledged that the Dartford money will be spent on transport projects in east London. Formal public consultation will begin next year.

A poll commissioned by the mayor showed 80% support for the new bridge among east London residents. Across the whole of London, 67% were in favour.

However, opponents argue it is a classic case of a new road which will create extra traffic. Susan Kramer, the Liberal Democrat candidate for mayor, another dissenter on Transport for London's board, said: "This bridge is almost on the scale of a motorway. The minute you allow traffic to come on to it, it will flood the local area." She claimed that even with a proposed £2 toll for non-local traffic, the bridge would quickly become a short cut for commuters from north Kent who drive to work in the City.