Power watchdog Ofgem was last night accused of posing a major threat to millions of pounds worth of green energy projects across the north of Scotland.

Scottish Renewables, the body that represents the wind and wave power industry, said several developments could be dropped because of proposals to increase transmission charges for remote generators.

Ofgem last month said it was "minded" to back the proposals, arguing that too much power is wasted in transmission, but has still to make a final decision.

James Ormiston, chief executive of Scottish Renewables, said: "At a time when the UK government's chief scientific adviser has said that climate change is the greatest threat to humanity, here we have the industry regulator penalising renewable electricity generators for generating where the resource is greatest.

"Ofgem wants to encourage more generation in the south of England while governments want more renewables to help tackle climate change. This is the proverbial square peg and round hole and it is time that Ofgem matches its decisions with climate change policy."

Scottish Renewables believes increased business rates and the proposed new transmission charges could eat up about a quarter of the income raised by wind and wave projects. That, Mr Ormiston said, made the benefits of several projects more "marginal".

He said: "In a world where capital is a very mobile resource, will Scotland be able to attract the investment needed to kick-start the potential of wave, tidal, biomass and offshore wind?"

His concerns were shared by the SNP and the Liberal Democrats.

Mike Weir MP, the Nationalists' energy spokesman at Westminster, said: "Ofgem has yet again proved it is prepared to undermine the Scottish renewable industries through its mad obsession with the theory of locational charges.

"Scotland has the potential to be the Saudi Arabia of renewable energy, but time and again Ofgem put obstacles in the way rather than promoting this vital national benefit. If these ludicrous proposals go ahead then future developments in wind, wave and tidal power may never get off the ground.

"You have to seriously wonder if this is a deliberate ploy to try and make nuclear generation in the south attractive to energy companies."

Renewables in the north of Scotland are far from uncontroversial. The enlarged power line from Beauly to Denny has sparked a major public inquiry with stiff opposition from local groups. Other lengthy transmission wires are also likely. Ofgem stresses mile after mile of pylons are not just unsightly. They are costly too.

The regulator last month said it favoured a system of "zonal losses" where remote generators would pay more to send their electricity to the national grid.