The Thames Array project for the world's largest offshore wind farm has today been given the green light and should be up and running by 2010.

The proposals for a 341 turbine wind farm capable of providing green energy for a quarter of London's homes, had faced opposition from the local Swale borough council that had delayed work starting on the project by 18 months.

However, a planning inspector overturned their objections towards an electricity substation and the project has finally been approved after a six week deadline for appeals against the decision expired this week.

Friends of the Earth welcomed the news claiming the scale of a project capable of delivering one percent of the UK's electricity needs indicated that it is possible for the UK to significantly increase its renewable energy generation.

"This is a landmark day for wind power in the UK," Tony Juniper, executive director at Friends of the Earth. "London Array really shows that dramatic cuts in carbon dioxide emissions are possible if we encourage investment in clean technologies."

But despite the last regulatory hurdle being overcome, celebrations at the consortium behind the scheme, which includes energy giants Shell and E.ON, are likely to be muted after reports revealed the 18 month delay has resulted in a massive legal bill and seen an increase in the cost of wind turbine technologies as global demand for parts has begun to outstrip supply.

According to reports in The Guardian the scheme is now likely to cost £2bn compared to an original estimate of £1.5bn.

The project is the latest in a spate of large scale clean energy schemes to receive positive news from the planning authorities in recent weeks. Last month plans for a £28m "wave farm" off the coats of Cornwall was given the green light, while the Scottish government also approved proposals from ScottishPower for a £10m wave farm designed to generate enough energy for 3,000 homes.

Keith Anderson, ScottishPower Renewables managing director, said the project underlined Scotland's potential as a "world leader in marine technology". But he warned that such technologies would only prove successful with continued support from government. "If we, as a nation, are to realise our renewables potential, and achieve our challenging renewable targets of 6GW by 2020, then the UK and Scottish Governments must continue to provide real commitment in terms of infrastructure, investment and political leadership," he said.

Meanwhile, long-standing plans for a barrage across the Severn Estuary designed to harness tidal power also took a step forward after a report from the Sustainable Development Commission signalled strong support for a project that could generate up to five percent of the UK's energy.

The recent developments were welcomed by Leonie Greene of the Renewable Energy Association, but she warned that despite the run of new project approvals many renewable energy investments were continuing to encounter a planning bottleneck.

"There are still long-term problems and these recent projects do not represent a sea change for the industry," she said. "The government is investigating streamlining planning processes, but currently there are still fundamental problems with planning and a lack of joined up thinking between different government departments on renewables."

She added that the focus on high-profile projects such as the Thames Array while welcome was also distracting from other forms of more localised renewable energy generation. "When you look at the potential for biomass, on site renewables and community scale projects the regulatory and planning framework is just not in place to encourage their adoption," she said.