Britain is wasting up to £1bn a year on subsidies for ineffective turbines, writes John Constable. 

Polly Toynbee suggested that government targets for renewable electricity will be missed because of mischievous Conservative planning committees ( Nimbys can't be allowed to put a block on wind farms, January 5). These, she said, were being herded by "media would-be squires" and other "rightwing commentators" who are, apparently, "rampantly anti-wind-farms" and "harbour an emotional support for the nuclear industry". But, in fact, this is not the problem, and her preferred solution - "new planning rules [which] will weaken local residents' right to raise aesthetic objections" - is simply irrelevant.

The cause of the failure to meet targets lies in a well-intentioned but poorly designed subsidy system, the Renewables Obligation (RO), which costs nearly £1bn a year. By failing to distinguish between the relative merits of different renewables, the RO has encouraged underperforming onshore wind turbines in low-wind areas (some less than 10% effective). Though of little engineering value, such plants attract speculators because they require smaller capital investment. The result has been to starve high-merit technologies of funding.

These faults are now widely recognised, and there is nothing inherently "partisan" in criticising the system or its outcomes. The DTI is currently undertaking a major revision to offer more subsidies per unit generated to offshore wind, biomass and tidal technologies. MPs and councillors from all parties are opposing obviously inappropriate applications for onshore wind.

Toynbee is correct in singling out offshore wind as a significant renewable technology. The irony is that this was one of the principal casualties of the RO, particularly regrettable since it can offer high wind resources close to centres of demand (ie London). It can also provide nearly twice as much electrical energy per unit of capacity as onshore wind.

Britain's green electricity targets are for the energy produced, not the capacity. But Toynbee seems to misunderstand this, writing that the wind farms "trapped in planning hell by local Nimbys amount to nearly the whole extra capacity needed to meet the 2010 target". The point is that large quantities of wind capacity in low-wind regions - most of England and Wales - would generate very little energy, and the targets will still be missed.

When the government drafted the 2010 renewables targets, it assumed a large proportion of offshore wind, with effectiveness well in excess of 35%. However, there has been almost no development effort in this technology.

Toynbee considers the Renewable Energy Foundation "an anti-wind outfit". We are not. We have consistently argued for offshore wind, among other technologies, to be made more attractive, and for a secure role for the renewables sector. Renewables have much to offer in tackling our energy crisis, but undiscerning enthusiasm, and an unwillingness to recognise the problems arising from a defective subsidy system, won't help anyone.

· John Constable is director of policy and research for the Renewable Energy Foundation research@ref.org.uk